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By J. Arthur Thomson 
What Is ManP 
Heredity 
The Outline of Science (Editor) 


Science, Old and N ew 


NOV13 1931 








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“AL ogicat SEWN 





By 


J. Arthur Thomson, M.A., LL.D. 


Professor of Natural History in the University of Aberdeen 


Author of ‘‘ What Is Man?” ‘‘ The System of Animate Nature,” 
‘Biology of the Seasons,” ‘‘The Wonder of Life,”’ 
‘** Heredity,” ‘‘ The Study of Animal Life,” etc 
Editor of ‘‘ The Outline of Science” 


G.P. Putnam’s Sons 
New York 8 London 
The Rnickerbocker Press 
1924 


Copyright, 1924 
by 
J. Arthur Thomsoa 





Made in the United States of America 


DEDICATED BY PERMISSION 
TO 


THE VERY REVEREND SIR GEORGE ADAM SMITH 
MoAt AD Dee Lid LITT. De P. B.A. 
PRINCIPAL OF THE UNIVERSITY OF ABERDEEN 


In GRATEFUL RECOGNITION 
OF 


NEVER FAILING ENCOURAGEMENT 


Digitized by the Internet Archive 
in 2022 with funding from 
Princeton Theological Seminary Library 


https://archive.org/details/scienceoldnewO0thom 


PREFACE 


THE science of Biology has naturally changed not a little 
since Darwin’s day. To appreciate the changes one may 
utilize a systematic treatise of recent date, and this is 
what every serious student must eventually do. But 
there is another method, which this book illustrates, that 
of selecting a number of arresting topics and discussing 
these in the light of recent advances. This is a more 
indirect method of gaining some understanding of the 
New Biology, but it is not less fruitful. 

Another motive underlies the studies here presented, 
that of continuing the disclosure of the unending interest 
of Animate Nature, even in everyday sights. One’s 
ambition, not, alas, one’s accomplishment, is expressed in 
Meredith’s line: ‘“‘You, of any well that springs, may 
unfold the heaven of things.’”” The book is full of fresh 
facts—mostly the discoveries of others; but not less im- 
portant is the presentation of these in a framework of 
personal reflections, some of which are fresh ideas in 
Biology. 

Studies I-XX have mainly to do with problems of 
Natural History or Ecology; Studies XXI-XXXIX 
are more strictly biological; Studies XL-XLV_ dis- 
cuss evolution questions; Studies XLVI-LII deal with 
man and his outlook. 

It is a pleasure to thank the proprietors and editors of 
The New Statesman, The Glasgow Herald, John o’ London's 


Vv 


vi PREFACE 


Weekly, Time and Tide, and the Illustrated London News 
for their courteous willingness that I should use, as a basis 
for these studies, various articles of mine which have 
appeared in their columns. 


J. ARTHUR THOMSON. 


University of Aberdeen, 
March, 1924. 


CONTENTS 


CHAPTER 


I.—SCIENTIFIC SNAPSHOTS 
II.—MAMMALS AND BIRDS OF THE MOUNTAINS 
II1I.—THE UNDERWORLD . 
IV.—A Visit To A Brrp-HILi 
V.—A NATURALIST’S PARADISE 
VI.—SEA SNAKES AND SEA SERPENTS 
VII.—THE ENCHANTED Woop 
VIII.—CaveE ANIMALS 
IX.—HERALDS OF SPRING 
X.—A SOCIETY SECRET 
XI.—ANTS AND PLANTS 
XII.—INSIDE AN AnTs’ NEST . 
XIII.—SLAVERY AMONG ANTS 
XIV.—BEETLES AND BUGS IN PARTNERSHIP 
XV.—INSECT MUSICIANS . 
XVI.—GARDENER INSECTS 
XVII.—TuHE FLOWER AND THE BEE 
XVIII.—Tue NAturAL History oF WAX 


XIX.—SHOWERS OF GOSSAMER . 
Vii 


IOI 


109 


123 
131 
139 
147 


Vill CONTENTS 


CHAPTER 
XX.—PEARLS AND PEARLS 


XXI.—THE PASSIONATE PIGEON 
XXII.—THE PROBLEM OF ANTLERS 
XXIII.—DANCING AMONG BirDs AND BEASTS 
XXIV.—MOTHERING AMONG ANIMALS . 
XXV.—MILK 
XX VI.—COMMENSALISM 
XXVII.—SyYMBIOSIS 
XXVIII.—OppITIEs OF DIET 
XXIX.—PLants LIVING IN INSECTS 
XXX.—THE CAT AND THE MOUSE 
XXXI.—THE DaNcinG MOUSE 
XXXII.—BIoLoGicaL DICHOTOMIES 
XXXITI.—Many INVENTIONS 
XXXIV.—THE CALL OF THE SEA . 
XXXV.—THE BEHAVIOUR OF INSECTS 


XX XVI.—SENSITIVE PLANTs . 


XXX VII.—CoLouR oF TROUT AND OTHER FISHES 


XXXVIII.—Livine Licuts 
XX XIX.—BACTERIA AND LUMINESCENCE 


XL.—THE AGE OF THE EARTH 


XLI.—How THE ELEPHANT GOT ITS TRUNK 


XLII.—THE ORIGIN OF LAND PLANTS 
XLIII.—THE ROMANCE OF THE WHEAT 


XLIV.—TowWarRDs SOCIALITY 


PAGE 


153 
161 
171 
181 
189 
197 
205 
213 
221 
229 
237 
243 
251 
261 
275 
277 
285 
295 
307 
315 
323 
331 
339 
349 
359 


CONTENTS 


CHAPTER 
XLV.—INBREEDING AND OUTBREEDING 3 


XLVI.—THE HumMAN HAND 
XLVII.—Man’s PLACE IN NATURE 
XLVIII.—TuHeE Hus oF CREATION 


XLIX.—INCREASE OF KNOWLEDGE, INCREASE OF 
SORROW 


L.—THE BEAUTY OF ANIMAL LIFE 
LI.—NATURAL HIsTtToRY AND MEDICINE 


LII.—TuHe New Natura HIstTory 





I 


SCIENTIFIC SNAPSHOTS 





SCIENTIFIC SNAPSHOTS 
The Young Earth 


As far as the eye could reach, a monotonous smoking 
desert, cindery under foot. Here and there out of a crack 
a sluggish crawl of molten rock, like very coarse-grained 
tar, hardening and blistering on the surface as it cools, 
and creeping out from beneath its crust in an ugly way. 
No sun by day, nor moon by night, nor any stars, but a 
thick curtain of cloud over everything. And beneath 
the cloud a heavy unbreathable air of carbonic acid gas 
and water vapour, much nitrogen, but only a trace of 
oxygen. There is no sign of life, nor any sound save 
crackling and hissing, and now and then a bomb. This 
was the surface of the cooling Earth—the future home of 
life—about 861 million years ago. 


The Dawn of Life 


A universal ocean, without continents or islands, but 
teeming with microscopic creatures swithering between 
plants and animals, more in a cubic foot of water than we 
can see of stars on a clear night. They move by living 
lashes; they trap the sunlight that struggles through the 
clouds; they feed on sea-water that is almost fresh and 
on the air that is mixed with it. Some of them grow 
and multiply by day, and die at night, for they have very 


3 


4 SCIENCE, OLD AND NEW 


slender resources. These were the first living creatures 
perhaps 500 million years ago. 

Ages pass; the floor of the sea has buckled here and 
buckled there; continents are formed with great deeps 
between. In the inshore waters, shallow enough to be 
weil lighted, some of the primeval forms of life anchor 
themselves, and grow out into long threads and broad 
plates—the first sea-weeds. But from among these 
emerges a new kind of life, minute predatory creatures 
that feed on the plants and on their fragments. They 
steal the plants’ munitions and explode them. These 
were the first animals, emerging, perhaps 400 million 
years ago. 


The First Birds 


A strange creature sprinting along the arid ground. 
It is a long-legged biped, about the height of a redshank, 
very spare and lightly built. It is like a bird in its sharply 
marked-off head, its supple neck, and its springy legs; 
it is like a lizard in its scales, its teeth, and its tail. As 
it runs it flaps its forelimbs, which bear a slight web and 
what look very like scales partly shredded up. After it 
gets some way on, it takes a long running leap, skimming 
over the ground. Occasionally, when a big reptile makes 
a clumsy feint at it, the startled creature leaps with a 
sharp cry on to a low-growing tree and disappears among 
the branches. This was the first bird—perhaps fifty mil- 
lion years ago. 


Life in the Great Abysses 


Vast undulating plains on the floor of the Deep Sea, 
like sand-dunes, but covered with slimy mud, treacherous 
to walk on. No scenery, no sound, no vegetation, not 
even rottenness. But many animals have colonised these 


SCIENTIFIC SNAPSHOTS 5 


inhospitable deeps, some anchored, others slowly swim- 
ming, as if half asleep, and others walking delicately with 
stilt-like legs on the ooze. Sluggish existences devour- 
ing one another in a grim sequence of reincarnations, but 
the last link of the chain depending on the ceaseless snow 
of moribund minutiz sinking through the miles of water 
from the surface overhead. 

There is enormous pressure, many tons on every 
square inch of the body, but it is not felt. The current 
of life flows slowly and centenarians flourish. There is 
no light, save the fitful gleams of luminescence from 
fixed animals that sparkle like Christmas-trees, and 
from free-swimmers gliding slowly past like illuminated 
miniature barges. Otherwise utter darkness. Also 
intense cold, near the freezing point, due to the down- 
sinking of icy water from the Poles. What an eerie 
world, covering 100 million square miles, more than 
half of the Earth’s whole surface, a world of eternal 
night and eternal winter, soundless, stagnant, and mono- 
tonous, a plantless world with a stern struggle for ex- 
istence! Such is the Deep Sea, with its insurgent animal 
life. 


The Bridge of Balgownie 


Before it becomes an estuary on a small scale the river 
has cut out a gorge, where the water flows sullenly. 
Just at the Bridge, where it turns sharply and meets the 
tide, there is a’ deep pool—thirty-five feet deep, the 
neighbours say. A sinister corner it often seems, with 
its steep sides so easy to slip down, so difficult to climb 
up, with strange whirlpool movements in the turbid 
water as if some huge creature was coiling and uncoiling 
itself down below, and with ugly flotsam drifting round 
and round on the oily surface. But the living is never 
ugly. The banks, with their trees and shrubs, make a 


6 SCIENCE, OLD AND NEW 


beautiful frame all the year round, and there are wild 
cherry trees, breaking into living foam in the Springtime. 
And one day, as we looked down from the bridge, we saw, 
darting up-stream, what looked like an arrow made of a 
bit of rainbow. It was a Kingfisher at the Old Bridge of 
Balgownie. 


The Courtship of the Blackcock 


On a shoulder of the hill a walled sheepfold, and beside 
it a level sward of short grass, surrounded by small 
alders and birches. In the half-darkness we hid in the 
sheepfold and arranged a peep-hole through the wall. 
At the welcome dawn two Blackcock arrive, and begin 
to strut about, calling loudly. As the sun touches them 
they are transfigured. The vermilion wattles above their 
eyes shine out vividly. Their dark feathers show a chang- 
ing play of blues and greens, and below the lyrate tail 
there is occasionally seen, like a flashlight, a great dazzle 
of silver. With hoarse cries the rivals rush at one an- 
other, jumping into the air, striking with beak and wings, 
raising the tail, scraping on the ground with their pinions. 
As the light grows, more jousters arrive, and the tourna- 
ment becomes very lively. 

By and by their desired mates, the Grey Hens, arrive 
on the scene, settling down quietly on the branches of 
the alder-trees. Their appearance strikes a new note; 
the tournament changes into a dance. Several cock-a- 
whoop males step on the stage at once, calling, jumping, 
fluttering their wings, and showing off till they are weary 
of their passion. It is a wonderful spectacle—the sun- 
rise, the growing light on the hills, the green sward, the 
transfigured birds, the bluffing and fighting, the dance 
and the display. Echoing the excitement, we raised our 
head above the wall to see more of the Mysteries. There 
was a sudden clapping of wings and a gust in the alder- 


SCIENTIFIC SNAPSHOTS 7 


trees, and the stage was empty in Glen Brora. Love’s 
Labour Lost that morning! 


The Ways of Stoats 


On the putting-green in front of us we saw a circle of 
larks and meadow-pipits, standing quite still, as if spell- 
bound. And so they were, for in the middle of the circle 
there were two stoats at play. They were gambolling 
madly, somersaulting, and making incredible living 
wheels of themselves. The birds stood around, pre- 
occupied and amazed. Had we been able to make our- 
selves invisible, there would soon have been two larks 
amissing, for there is a method in the stoat’s madness. 

In front of us, in the fairway of the links, we saw a 
stoat going very slowly, which in itself was puzzling, 
for they usually lope over the ground at a great pace. 
We had to hurry on; we cried “‘Fore’’; we could not but 
overtake the leisurely stoat. And then the puzzle solved 
itself. For it was a mother-stoat, taking her youngster 
for its first walk—a youngster so tender that it could not 
run. Just as we were upon them, the mother seized the 
young one by the nape of the neck, ran swiftly forward, 
laid it carefully in a bunker, and then came to meet us! 































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MAMMALS AND BIRDS OF THE MOUNTAINS 





MAMMALS AND BIRDS OF THE MOUNTAINS 


EVERY typical mountain shows three zones—first 
the forest and woodland, then the treeless steppe tracts 
with varied herbage and often with good pasture on shelves 
and plateaux, and then uppermost the relatively barren 
heights with ‘‘alpines’’ and lichens, like the tundra of 
the low moorland and plain. So if we try to take a 
survey of the tenants of the mountains, we can profitably 
distinguish those of the forest, such as bears; those of the 
Seppe tracts, such as wild sheep and goats; and those 
of the sparsely clad uppermost stretches, such as the 
marmots of the high Alps. 


Relict Mountain Animals 


But we would suggest, for North Temperate countries, 
another grouping which is not less instructive, and is, 
in a way, more interesting. We may divide the tenants 
of the mountains into the relicts, the insurgent colonists 
and the refugees. By the relicts we mean the survivors 
of the Arctic or glacial tundra fauna that once extended, 
on the low grounds, from the north far into Central 
Europe. When the climate became milder and the 
glaciers retreated, many of the northern animals left 
their bones in the south. It was too mild for them. 


II 


12 SCIENCE, OLD AND NEW 


Others, like the reindeer, probably managed to trek 
northwards, but others went up the mountains. Those 
who followed the last alternative are our relicts. One of 
the best examples of this is the little snow vole, which 
rarely descends below 4,000 feet, and goes up to the very 
summits. It has a tough constitution, it burrows be- 
neath the snow from one root to another, it stores for the 
time of bitterest scarcity. The snow vole was originally 
a tundra mammal, but it has conquered the great heights 
and found an area where it has no enemies. Similarly, 
the marmot was once a tenant of steppe-land; its bones 
are found in low-ground caves and as far south as Gratz; 
but now it is at home in very inhospitable places in the 
Alps. It burrows, it stores bedding and blankets at least, 
it is quick to sound the danger signal—whistling through 
its teeth—and it circumvents the winter by sinking into 
sleep. Or, again, there is the mountain hare or blue 
hare, first cousin of the common maukin, but a distinc- 
tively northern species. In glacial and inter-glacial 
times it came far south in the low grounds; when a milder 
climate set in, some migrated and others climbed. So 
on the mountains this relict holds its own to-day, safe 
in its elusive roving, in its ability to thrive on short 
commons (nibbling at lichens when hard pressed), in 
its quiescence during the day, and in its winter assump- 
tion of a white dress which conserves the precious animal 
heat and gives the creature a Gyges ring, on a snowy 
background at any rate. As a bird to cap the mountain 
hare we may take the ptarmigan, famous for its three 
moults in the year. It is a northern bird, but in the more 
southerly part of its range it is strictly confined to high 
altitudes. Even in Scotland it has disappeared from the 
southern countries. On the mountains of the Highlands 
this non-migratory relict keeps its foothold. It can 
subsist on berries and shoots; it has a heart suited to the 
strain of living at a high altitude (far stronger than that 


MAMMALS AND BIRDS OF THE MOUNTAINS 13 


of its cousin, the willow grouse of the Lowlands); it 
turns white in winter; and perhaps there is a touch of 
perfection in the way it moults its worn claws and finds 
fresh ones ready underneath. 


Insurgent Colonists of the Mountains 


The second contingent of mountain animals consists 
of insurgent colonists from the steppe-lands, which found 
it practicable to make a living at considerable altitudes, 
especially where there are shelves and plateaux with good 
soil. Just as the industrious Swiss migrate in the sum- 
mer to their ‘‘alps,’ and feed an astonishing number 
of cattle on these high mountain shelves, so many animals 
have done. The chamois is nowadays a mountain- 
loving antelope, but it was probably, to begin with, a 
tenant of the Asiastic steppes. It is hardy; it is alert to 
sense danger and give the social signal by whistling 
or stamping; it has a thick coat and a woolly under-vest; 
its hoofs are well suited for gripping the rocks, the outer 
edges being higher than the sole. Everyone knows how 
it disappears up what seems to the amateur an unscale- 
able mountain-side, or hurls itself down a precipice and 
looks up blandly from below. If we understand the 
chamois as an insurgent colonist from the low grounds, 
we understand a score of others, from the goral of Indian 
altitudes to the so-called Rocky Mountain goat which 
ascends to the loftiest peaks. Bovine animals belong 
to the plains and steppes, but the grunting yak of Tibet 
ascends to 20,000 feet. This black ox, as agile as it is 
strong, extraordinarily shaggy and Spartan, seems to 
delight in enduring hardness. Valued for hide and 
flesh and milk, it adds to its virtues in being docile. It 
is an unspeakably enduring beast of burden—crossing 
glaciers, pushing through snow-drifts, and fording ice- 


14 SCIENCE, OLD AND NEW 


cold torrents. It is a creature of the plains that has 
mastered the mountain-steppes, and if we understand 
the yak we also understand the numerous kinds of wild 
sheep and wild goats—the unlucky ibex of the Alps and 
the fine markhor of the Himalayas. It is the law of 
life to look out for niches of opportunity, and these in- 
surgent colonists have found not merely a niche, but a 
shelf. Doubtless there have been many who tried whose 
constitutions failed to stand the rigorous tests. We have 
also to remember the age-long conflict between carni- 
vores and herbivores, and the continual tendency of the 
latter to retreat before the former. To the sheep and 
goats the discovery of the mountain-shelves meant not 
only pasturage but safety—safety for a while, till the 
forest carnivores followed them; and so we understand 
the snow leopard and the mountain puma. 

Let us take two birds for a change. Many are familiar 
with our long-billed tree-creeper, which runs up the stem 
like a mouse, stopping at short intervals to probe insects 
out of the crevices of the bark. A relative of this inter- 
esting bird is the beautiful rock-creeper of the precipitous 
cliffs. It falls down the face in zig-zag lines, checks 
itself by spreading its beautifully coloured wings; it 
ascends in jerks, opening and closing like a big butterfly, 
and picking out small insects and spiders with its long 
curved bill. If we understand the rock-creeper’s coloniza- 
tion we have the key to Alpine accentor and Alpine 
swift, to rock thrush and snow finch, and more besides. 
We referred a moment ago to insurgent carnivorous 
mammals like the snow leopard, and we should place the 
golden eagle on the same platform—as a colonist of the 
heights, following such creatures as the grouse and the hare. 
To some extent doubtless it is also a refugee, for it is a 
slowly multiplying bird, and a bit of a specialist in its 
diet. It lives dangerously and naturally seeks safe 
retreats. 


MAMMALS AND BIRDS OF THE MOUNTAINS 15 


The Refugees 


The third set of mountain animals includes the refugees, 
hard-pressed creatures which have sought out an asylum 
—a way of escape from the too intense competition of the 
crowded low grounds. ‘This is well illustrated by the 
coneys or hyraxes of Africa, Palestine and Syria. They 
are small animals, ‘‘a feeble folk’’; they are not very 
quick and not very clever—wary rather than ‘‘wise’’; 
they have little in the way of weapons or armour; and 
they do not burrow. What chance have these old- 
fashioned creatures, almost anachronisms? Some of 
them have saved themselves by becoming arboreal, and 
the others by ascending the mountains, even to 10,000 
feet. They have thick coats that ‘keep out the cold,”’ 
and their feet are well adapted for scrambling among 
the rocks. Another refugee is the desman of the Pyrenees, 
an extraordinary bundle of curiosities, that occurred 
long ago in Britain. It is about five inches long in body 
and as much again in tail; it has a very mobile proboscis 
like the beginning of a miniature elephant’s trunk, which 
it twists round its food. It is said to be able to put it 
into its mouth. Now this creature belongs to the dwin- 
dling order of Insectivores—a primitive group of mammals 
—and it keeps agoing as a refugee on the heights. In 
fairness we must add that it has also become aquatic, 
like our own water shrew, and that it is likewise a bur- . 
rower. If we understand the desman’s story, we also 
understand the Alpine shrew, the Tibetan mole-shrew, 
and the Himalayan swimming shrew; all are refugees. 

Writing at the age of sixty-two, Ruskin said that though 
he had spent much time beside torrents, he had never 
seen a water-ouzel alive! This was an extraordinary 
statement, for the beautiful bird is very widely distributed 
throughout Britain on quickly-flowing streams that ripple 
over stones. It is particularly fond of mountain streams 


16 SCIENCE, OLD AND NEW 


and may be seen or heard at a level of 5,000 feet. Now 
the point is that the water-ouzel is a near relative of the 
wrens which has become aquatic. It walks on the bed 
of the stream, gripping with its toes, and it also uses its 
wings in a sort of underwater flight. It feeds on small 
water animals, and makes a domed nest of grass and moss 
under a waterfall or in some such safe place. The male’s 
wren-like song may be heard in mid-winter, sounding 
so cheerily from a stone on the mountain stream that we 
wonder if the word conqueror would not have been better 
than refugee. 

Let us take a clearer case to end with—the North 
American mountain beaver. This is a primitive rodent, 
almost ‘‘a living fossil’ —a short-tailed, blunt-snouted, 
chunky creature rather over a foot long, grey to black in 
colour. It is a timid, slow-going animal, with a cumber- 
some gait, so leisurely that a child can catch it. It is dull 
of sight and hearing, and it has no voice except a noise 
made by rasping the lower incisors sideways across the 
tips of those above. Everything is against the survival 
of this anachronism, and yet it holds fast. When we ask 
‘how?’ the answer comes: it is elusive, nocturnal, a 
burrower, a storer of varied vegetable food, a social 
creature, very sensitive to touch and keen of smell. But 
to our thinking, part of the answer would be left out if 
we did not add that it goes up the well-clad hill slopes 
to 6,000-8,000 feet. The mountain beaver is a successful 
refugee. 


III 
THE UNDERWORLD 


17 








“t. ¢ SARL Se aie 






THE UNDERWORLD 


THERE seems to have been a persistent endeavour on 
the part of animals to get out of the water on to dry 
land. In various ways it has been to them age after age 
an El Dorado—to some a place of safety, to others a less 
crowded home, to some a freer air, to others more abun- 
dant food. Thus, after plants had prepared the way, the 
dry land was invaded by successive contingents of ani- 
mals—such as earthworms, centipedes, and amphibians, 
each great invasion with far-reaching consequences. 


Difficulties of Terrestrial Life 


But after adventurous pioneers of various races of 
animals had reached the promised land, they discovered 
that it was not always flowing with milk and honey. 
In water they could move freely in any direction in three 
dimensions; on land they were restricted to one plane— 
the surface of the earth. In the sea they could lay their 
eggs almost anywhere in the universal cradle of the waters, 
unless the struggle for existence was terribly keen; on 
land they had to hide the eggs, or bury them. Often 
the only solution of the difficulty was for the mothers to 
carry the young ones about with them before birth or 
after birth, not parting with them till they were more or 
less able to fend for themselves. Thus we see many a 
spider carrying about her eggs, and by and by her young 

19 


20 SCIENCE, OLD AND NEW 


ones, in a silken bag. The kangaroo puts its very help- 
less, prematurely born, young ones into an external 
pouch, and it is quaint afterwards to see them going out 
and coming in. 

The essential point is simply this, that the conquest 
of the dry land involves risks of drought and frost and 
overcrowding; there are no currents to bring food near; 
the abundant oxygen is more difficult to capture. There- 
fore it became necessary for some of the colonists to trek 
once more; some became arboreal and others got into the 
air; some became cave-dwellers and others, which we wish 
now to study, burrowed beneath the ground. 


The Worm Invasion 


There is a strong probability that earthworms sprang 
from a fresh water stock, which in turn had been started 
by migrants from the sea. Many not very distant rela- 
tives of earthworms are to be found in fresh water, and 
there are several genuine earthworms, like Alma and 
Dero, which possess gills. It is likely then that migrants 
from fresh water became burrowers beneath the surface 
and had for a time a Golden Age—a world of their own 
and plenty of food. As ages passed, however, the centi- 
pedes followed the earthworms underground, perhaps in 
the Carboniferous Period, and these continue to be their 
inveterate enemies. Then came burrowing carnivorous 
beetles. There is also in Brazil a carnivorous Planarian 
worm which follows the earthworms into their retreats, 
and in many countries the carnivorous slug (Testacella) 
does the same. Ages afterwards there were moles. Thus 
the earthworms have become a much persecuted race— 
their Golden Age long since over. How do they survive at 
all? They have become nocturnal; they are exquisitely 
sensitive to vibrations; they can grow a new tail or even a 
new head if what they had is cleanly bitten off. 


THE UNDERWORLD ai 


The Fitness of the Mole 


What a compact bundle of adaptations is a mole! Its 
shape is suited for tunnelling, its snout for thrusting and 
probing, its short muscular neck for tossing up the loose 
earth. Its shovel-like hands are broadened out by an 
extra sickle bone, and the muscles of the pectoral girdle 
are those of an athlete. It literally swims beneath the 
ground, and can turn through 120 degrees in four strokes. 
Negatively, it has no projecting ear-trumpet, for that 
would be in the way; the rudimentary eye is well protected 
with hair, so that it is not scratched; there are arrange- 
ments for keeping the earth out of the nostrils and the 
mouth. The hair has no “‘set”’ so that it is not ruffled 
when the animal moves backwards, and it is very readily 
kept clean. The mole is an extraordinarily strong and 
active animal, with a big appetite and unsurpassed rapid- 
ity of digestion; it is no coincidence that its staple food 
consists of earthworms, which are very abundant. In 
winter it can burrow below the grip of the frost’s fingers, 
and it also makes caches of decapitated earthworms to 
serve as a last resource. Has not the mole conquered the 
underground world? 


A Survey of Subterranean Animals 


Until we look into the matter we do not realize the 
number and variety of subterranean animals, living like 
sappers and miners out of sight. There is sometimes a 
literal truth in the phrase ‘“‘the living earth.” Not very 
much is yet known of the Protozoa of the soil, the amcebe 
and infusorians that live in damp earth. They are some- 
times of agricultural importance, for instance, by devour- 
ing large numbers of the bacteria which bring about de- 
composition or other useful chemical changes in the soil. 

At a much higher level are a few subterranean Planarian 


22 SCIENCE, OLD AND NEW 


worms and numerous threadworms which pass the whole 
or part of their life underground. Many of these thread- 
worms are notorious for their destruction of garden pro- 
duce and field-crops, and they are the more formidable 
because of their capacity for surviving prolonged drought. 
They lie inert and even brittle, month after month, even 
year after year, showing no sign of being alive, and yet 
not dead, as is shown by their reawakening when the 
rains return and the soil is once more moist. 

The general significance of subterranean life is clearly 
illustrated by the larve of various terrestrial insects. The 
adults are usually able to fly, but they lay their eggs in the 
safety and moisture of the ground, and the larve live there 
for months or even for years, feeding on the roots of plants, 
and accumulating energy for the adult reproductive period 
when feeding often counts for little. The tough larve of 
click-beetles, known as wireworms, do incalculable harm 
in devouring the underground parts of plants, and it is 
difficult to discover any counteractive. Leather-jackets 
are the subterranean maggots of the cranefly or daddy- 
long-legs, and it is a not uncommon sight to see the rather 
graceful insect struggling out of the pupa-case which the 
larva makes just at the surface of the soil. 

A different rank must be given to a number of adult in- 
sects that have become subterranean, such as some ants 
and termites, which dislike the light of day, and little 
small-eyed Staphylinid beetles, which are found only in 
the burrows of moles and hamsters. A very interesting 
miner is the mole-cricket (Gryllotalpa), a clever burrower 
with enormously strong fore-legs very suggestive of those 
of the mole. The list of backboneless burrowers includes 
two blind centipedes and a blind millipede. There are also 
some snails and slugs which go deeply into the ground. 

When we pass from backboneless to backboned animals, 
we find a temporary burrower in the African mudfish 
(Protopterus), which buries itself in the earth when the 


THE UNDERWORLD 23 


pool dries up, keeping its mouth at the foot of a narrow 
pipe that goes up to the surface. It may spend more than 
half the year in a lethargic state, and it is sometimes 
safely transported to London inside its mud-nest, which 
is then dissolved away to liberate the fish. 

Certain old-fashioned amphibians, the blind Czecilians, 
have sought refuge underground, and have assumed an 
earthworm-like appearance without any trace of limbs. 
Unlike frogs and newts, which are quite naked,-. these 
Cecilians have minute scales imbedded in their skin, and 
this is one of the archaic features linking them back to a 
remote scale-bearing ancestry. Another interesting point 
is that the unhatched young have gills—a shunting back- 
wards of a feature which would appear later if the Ceci- 
lians spent their youth in the water after the fashion of 
ordinary amphibians. 

It is rather striking to take one of these Caecilians and 
place beside it a burrowing limbless lizard (an Am- 
phisbeenid) and a burrowing snake (say Typhlops), three 
animals belonging to very different groups, one an amphi- 
bian and the other two reptiles. Yet they are extra- 
ordinarily like one another externally—they show an 
earthworm-like cylindrical body, no trace of limbs, and 
minute, hidden, or degenerate eyes. Moreover, the big 
ventral scales which ordinary snakes use in gripping the 
ground are replaced in burrowing snakes by small scales 
like those which cover the rest of the body. Such super- 
ficial resemblance between unrelated animals is called 
‘“‘convergence’’; it means that different kinds of animals 
have come to be similarly adapted to similar conditions 
of life—in this case, burrowing underground. 

A burrowing bird seems almost like a contradiction in 
terms, and yet, besides the sand-martins which make 
yard-long tunnels when they nest, besides the puffins and 
shearwaters and stock-doves that utilize the holes made by 
rabbits, there is a burrowing parrot (Stringops) in Australia 


24 SCIENCE, OLD AND NEW 


which has given up flight altogether. Associated with this 
strange new departure there is a loss of the keel on the 
breastbone—the keel to which the muscles of flight are 
in part attached in ordinary birds. It is strongly devel- 
oped in birds of powerful flight; it is absent in the flight- 
less running birds; and we find it difficult to answer the 
evolutionist’s conundrum: Did the burrowing parrot lose 
its keel because it took to burrowing, or did it take to 
burrowing because it was losing its keel? 

What strikes us first in regard to burrowing mammals 
is that the habit has been resorted to over and over again 
by different types. There is the so-called marsupial mole 
of Australia; there are insectivores, like the archaic golden 
mole of Africa, the Scalops of North America, and the 
common mole of Europe; there are rodents like the prairie 
dogs of North America, the viscachas of South America 
and the Spalax of Europe. 

A second fact that stands out is that these diverse mam- 
malian burrowers have a good deal in common—a cylin- 
drical shape, short strong limbs, short soft fur, a short tail 
or none, an absence of projecting ear-trumpet, and small 
or degenerate eyes. In other words, the burrowing mam- 
mals show similar adaptations to similar conditions of life. 
To suppose that burrowing mammals lost their ear- 
trumpet or pinna as the direct consequence of burrowing 
—rubbing it off, as it were, in the course of many genera- 
tions, would be to take a very rough and ready view of 
evolution. The size of the ear is a variable character, as 
we see among ourselves; the probability is that those bur- 
rowers whe varied in the direction of small ear-trumpets, 
and then none, would get on better than those with 
prominent ear-trumpets—which would be likely to be- 
come scratched and sore. The small-eared variants 
would gradually become the type of the race. There is 
an important calculation made by Professor Punnett, 
that if in a population of animals there were 0.001 per cent. 


THE UNDERWORLD 25 


of a new variety, and if that variety had even a five per 
cent. selection advantage over the original form, the latter 
would almost completely disappear in less than a hundred 
generations. Apart from the risk involved in ear-trumpets 
that they would tend to become sore, and apart from the 
fact that big flaps would be in the way when it is important 
to reduce friction, it should be noticed that the use of the 
ear-trumpet is to collect the waves of sound in the air and 
aid in their localization, and that this purpose could not 
be served underground. We see the donkey moving his 
long ear without moving his head; we move our head with- 
out moving our ear; therefore our ear-trumpet is small 
compared with the donkey’s. 


The Ant-Lion 


Animals have sought out many inventions, and one of 
the most original is to the credit of the larva of the ant- 
lion. The adult is an elusive flying insect, distantly re- 
lated to dragonflies; the larva is a burrower of sorts. In 
sandy places it moves round and round backwards and 
excavates a funnel-shaped pitfall about the size of an 
ordinary watch and about an inch deep. At the foot of 
this widely open shallow funnel the ant-lion larva hides 
itself with the sharp tips of its jaws slightly projecting. 
Inquisitive ants come to explore the pitfall; they lose their 
footing on the treacherous slope; they tumble down and 
are seized by the ant-lion, who sucks the sparse juices of 
their body. Not less striking is the shaft sunk by the 
female Trapdoor spider as a safe hiding-place for her 
eggs and young. 

We see, then, that in a great variety of ways diverse 
animals of low and high degree have sought refuge under- 
neath the ground, sometimes in the interest of self-preser- 
vation and sometimes in the interest of race-continuance. 
Of the strange company, with this tn common that they 


26 SCIENCE, OLD AND NEW 


inhabit the underworld, Mr. Edmund Blunden gives us a 
glimpse in his incomparable fashion: 


I am the god of things that burrow and creep, 
Slow-worms and glow-worms, mould-warps working late, 
Emmets and lizards, hollow-haunting toads, 

Adders and effets, ground-wasps ravenous; 

After his kind the weasel does me homage, 

And even surly badger and brown fox 

Are faithful in a thousand things to me. 


IV 


ASV ISI Te TOSASBIRD-HiEL 


27 





A VISIT TO A BIRD-HILL 


ONE of the difficulties in telling of great sights—such as 
a bird-hill with its million birds—is the incredibility of the 
truth. Even in restrained approximations the cold- 
blooded listener hears the twang of the long bow. That 
must be felt by every visitor to one of the Scottish bird- 
hills, Handa Island; what one sees is incommunicable, 
and between the two timidities of telling the incredible 
truth and making a ridiculous under-statement, one is 
inclined to say nothing at all. But let us take our courage 
in both hands! 

Handa lies about a mile off Scourie, and Scourie is al- 
most the end of the world—how very far from the end of 
comfort and kindness those who stay there will soon dis- 
cover. It is true that Scourie, which lies on the west coast 
of Sutherland, is relatively inaccessible, for it is about 
forty-five miles from the nearest station (Lairg on the 
east), but it makes up for this and a certain lack of re- 
straint in its meteorological conditions by being near 
Handa, and by being encompassed by great mountains. 

To get to Handa one offers libations to Neptune and 
gifts to AZolus, selects the finest day in the year (July 7th, 
1922), makes friends with two skilful mariners, and sets 
sail, not unprepared for the swell on a sea which is open 
water to Greenland, and for a ‘‘jabble’”’ of water where 
Loch Scourie opens into the Sound. On the voyage, which 
may last an hour, one sees plenty of birds on the water. 


29 


30 SCIENCE, OLD AND NEW 


There are furtive green-eyed cormorants which look as if 
they had a guilty conscience, darting their bill nervously 
in all directions; unabashed puffins, with their moultable 
bill like a coat of many colours, which allow us to come 
quite close and then fly along the surface with much 
spluttering; and confident guillemots which dive through 
a roller and look at us from the other side. We asked the 
skipper quite politely to try to keep the boat along the 
hollows, but he paid no heed to our suggestion. 


The Hill Itself 


Handa is built of stratified conglomerate and sand- 
stone, of Torridonian age, in great contrast to the tangle 
of older Archzean or Lewisian gneisses and schists on the 
mainland, which come, we believe, very near the original 
crust of the earth, and are almost terribly weathered 
down. Everywhere there are glacial striz and smoothed 
hummocks; almost everywhere there is gaunt nakedness 
except in the troughs between the ridges where a shallow 
soil has accumulated or a peat-bog has been formed. We 
do not suppose the appearance of things has changed 
much since the last Ice Age. 

Handa has a long grassy slope towards the mainland 
and precipitous cliffs to the north and west. To the north 
it looks—from a long distance—on Greenland, to the west 
on the Butt of Lewis and the hills of Harris. The island 
feeds about three hundred sheep and many rabbits. There 
used to be a few houses, but now there is only a shelter 
for the shepherd who comes over for six weeks at lambing 
time. ‘There is a cache of oatmeal and tea for travellers 
who are marooned on the island by mist or storm. Like 
the widow’s store, it is never exhausted. 

We saw nothing remarkable on the long grassy slope— 
numerous ‘“‘chacking’’ wheatears with brilliantly white 
rump feathers, besides insistent whinchats, plenty of 


A VISIT TO A BIRD-HILL 31 


larks and heather linties or twites. Here and there a 
circle of small feathers on the short grass told of a hawk, 
and perhaps it was a crow that accounted for that freshly 
picked rabbit’s skeleton. There were the characteristic 
flowering plants—butterwort and milkwort, bog-myrtle 
and sundew, marshwort and scented orchis. At the top 
of the bird-cliffs the sea-pink grew in great tussocks of 
root-work sometimes raised a foot off the richly manured 
ground. There was no heather out (July 7th) and the 
distant hills showed snow in some of their northward 
corries. 


The Shelves of Birds 


We were lucky enough to have as our guide the village 
schoolmaster—would it be wresting words to call him the 
genius loci?—who showed no little art in leading us always 
from the great to the greater on a crescendo plan. We 
came suddenly on a precipitous sea-cliff a hundred and 
fifty feet high, built up like a giant’s book-case of succes- 
sive sandstone shelves, from a foot to a foot and a half in 
breadth, and on these shelves there were tens of thousands 
of birds, often packed so closely that their bodies were 
touching and their necks crossing. In most cases the 
various kinds were quite separate, living, as it were, in 
different streets of Clifton. A common succession was 
this—lowest down, a kittiwake area; then a guillemot or 
razor-bill section with perhaps thirty shelves one above 
the other, and then at the top, where the turf began, the 
burrows of puffins. In some cases there would be a section 
of rock-face with guillemots only; in other places there 
were more razor-bills, easily distinguished from their 
cousins by compression of the bill from side to side; here 
and there a kittiwake had established a claim to an iso- 
lated broad bracket of rock and sat there on its nest 
surrounded by thousands of guillemots. We went higher 


32 SCIENCE, OLD AND NEW 


and higher, along the top of the escarpment, till the face 
of the cliff for three hundred yards or more was four 
hundred feet high, but everywhere the scene was essen- 
tially the same—long terraces of kittiwakes, guillemots, 
razor-bills, and puffins. In some places the guillemots and 
razor-bills were able to stand upright with their immacu- 
late white breasts turned seawards, but most had their 
back outwards and pressed their body against the rock. 
The long webbed feet must be of use in gripping a down- 
ward sloping shelf, but the advent of an extra guest from 
the sea often overtaxed the capacity of a crowded corner 
and considerable dislodgment and altercation ensued. 
We saw many fights and heard much wrangling and mur- 
muring, but the general impression was quite the other 
way. It looked as if there was much give and take, and 
though the noise was sometimes deafening, it sounded 
more like good-humoured gossip than quarrelling. One got 
an impression of general well-being, and the suggestion 
of repletion made one think of the multitude of fishes 
that must be needed every day to keep up the aplomb 
of the colony. Sometimes, we do not know why, the 
clamour changed its character and sounded querulous, 
a little like the tuning up of a hundred thousand bagpipes. 
The atmosphere reminded us of Emerson’s remark about 
the average man that he had too much guano in his com- 
position. 


Birds and Man 


To our presence the birds seemed quite indifferent, 
doubtless because of a well-established tradition of 
security. Shooting and collecting are nowadays rare at 
Handa. In a re-entrant angle between two cliff-faces 
there is a lofty isolated stack with a grass-covered flat 
top, which used to be moving with puffins. There are 
none now except along the edge, and the explanation 


A VISIT TO A BIRD-HILL 33 


offered is this. Some years ago a party of fishermen- 
collectors came over from the Lewis and slung a strong 
rope across the re-entrant angle and right over the top of 
the isolated stack. It makes one’s flesh creep to hear that 
they crossed by the rope hand-over-hand to the top of 
the stack, where they made things easier by fastening 
the rope to three poles, two of which are still standing. 
For sound economic reasons they cleared off the puffins 
in bags—there is a yarn about using trousers—and the 
level summit of the stack has been untenanted ever since. 
It got a bad name; it remains taboo to the generations 
of puffins. 


The Life of the Birds 


With a field-glass it was easy to watch individual birds, 
to see the preening, the caressing, the bickering, and to 
distinguish the young birds from their parents. Almost 
all the youngsters were ready to fly away, and we were 
lucky in not arriving the day after the fair. Some evening 
soon the crowds will become restless; the migratory im- 
pulse will begin to work; and in a short time the streets 
of the city will be desolate as far as guillemots, razor- 
bills, and puffins are concerned. Most of them spend 
the winter in the open sea and off the coasts of southern 
lands. The cormorants that we saw on broad shelves at 
the foot of the cliff, a few feet above the water, are prac- 
tically residents in Britain, and so are the kittiwakes 
and other gulls. But the essence of the great sight is that 
the shelves of the cliffs afford a convenient and secure 
summer breeding-place, especially for the three members 
of the auk family—the guillemot, the razor-bill, and the 
puffin. 

We say secure, because the birds have almost no ene- 
mies. The sea-eagle or erne is now extremely rare; the 
buzzards which still frequent Scourie can hardly venture 


34 SCIENCE, OLD AND NEW 


among the legions of sharp-billed guillemots; and it is 
improbable that the rapacious Great Black-Backed Gull, 
who was much in evidence, gets more than the weaklings. 
It is probable that some young birds tumble off the 
shelves, or are killed in the course of their education, but 
one gets the impression that in spite of the abundance of 
life there is not much death. One must remember also 
how Darwin showed that the top-like shape of the single 
egg of the guillemot or the razor-bill allows of rotation 
without rolling, should it be jostled by the wind or by the 
parent’s feet. 

Having shown us the 4oo feet cliff-face with perhaps 
400,000 birds, our guide was wise enough not to let us 
down gradually. He took us to a gigantic, unsunned, 
dark-walled Devil’s Pot-hole, perhaps 250 feet deep, 
with the sea rolling in by two openings at the foot, and 
there we saw no birds at all. All along the escarpment 
it seemed that the birds avoided dark and damp places. 
There were other untenanted sections which seemed to 
us suitable enough, but some, at least, of these showed 
evidence of the dislodgment of great slices from the rock’s 
face. This would give the section a bad reputation. 

Having greatly enjoyed our impressions of the abun- 
dance, the gregariousness, the adaptability, the resource- 
fulness, and the victoriousness of life, we climbed to the 
grassy summit of the island and saw on the mainland the 
amphitheatre of great mountains—one of the most magnif- 
icent views in Britain—from Sulven, Canisp and Quinaig 
in the south to Ben More of Assynt, and from the massive 
cone of Ben Stack, past Arkle, Fionne Bheinn (2,980 
feet), and Spionnaidh to Grianan, beyond which lies 
Cape Wrath. We eventually remembered the patient 
boatmen down below, who rowed us back—wind and tide 
against them—to a hospitable roof, but very late for 
dinner. 


Vv 


A NATURALIST’S PARADISE 


35 







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A NATURALIST’S PARADISE 


THERE is an island in the heart of the Everglades of 
Florida which bears the attractive name of Paradise Key, 
and the account of it given by Mr. W. E. Safford in the 
Report of the Smithsonian Institution for 1917 warms 
the naturalist’s heart. It is a sub-tropical jungle within 
the limits of the United States. The primeval conditions 
of animal and plant life have remained unchanged by man, 
for the clearings and fires and drainage which have 
greatly altered many of the Everglade Keys have left 
this one untouched. Apart from certain insects and 
poisonous plants, every prospect pleases; and the collec- 
tor finds a closed door, for Paradise Key is now a State 
Park and a three-mile-square sanctuary for living crea- 
tures, plants as well as animals. 

The Everglades of Southern Florida represent a re- 
cently raised area of the sea-floor, and consist in great 
part of marshes and sloughs and shallow ponds, with 
lime-stone rock cropping up here and there, giving a 
foundation for trees. During the rainy season of the 
warmer part of the year the Everglades are flooded; in 
the dry winter months they can be crossed on foot. 
Along one border of Paradise Key there is a deep slough 
which never dries up, and this gives a particular stability 
to the bionomic conditions and greatly lessens the risk of 
fire. 


37 


38 SCIENCE, OLD AND NEW 


Exuberant Vegetation 


From Mr. Safford’s report we get, first of all, an im- 
pression of the abundance of vegetative life. There is a 
mingling of temperate persistence and tropical exuberance. 
The deep slough is crowded with water plants, yellow 
water lilies, water arums, whose leaves and roots, like 
those of the British cuckoo-pint or jack-in-the-pulpit, are 
crammed with needle-like crystals ‘‘which burn the 
mouth like fire,’ pickerel weed or Pontederia with spikes 
of blue flowers, besides Sagittarias, ‘‘floating hearts,” 
bladder-worts with traps for small crustaceans, and many 
kinds of aquatic grasses and sedges. The ‘‘saw-sedge”’ 
is one of the guardians of the Everglades, its margins 
and keel thickset with very fine and very sharp teeth. 
Out of the water are the marsh-loving plants, the am- 
phibious willows, the swamp bay smelling of bayrum, 
the wax myrtle from which candles can be made, the 
white-flowered magnolias with silver lined leaves, besides 
mangroves with their stilt-like roots and small groves of 
cypress. On the more solid ground are trees—the magnif- 
icent live oak of the Southern States, ‘‘which sometimes 
spreads its moss-covered branches over an area 200 feet in 
diameter’’; the gumbolimbo, which exudes fragrant bal- 
sam when it is wounded; the golden-brown satin leaf; the 
laurel-cherry, with leaves rich in prussic acid; the wild 
tamarind with fern-like foliage; the wild olive, and the 
pigeon-plum. Even the names transport us into a land 
of pure delight—the paradise tree, the myrtle-of-the-river, 
the marlberry, and the bois-fidéle (incorrectly translated 
“fiddle wood’’). Another note is struck, however, by 
the great poison-tree, a giant sumach, the sap of which 
acts like the poison ivy of some American woods, or like 
the milky juice of another sumach that furnishes the 
almost indestructible, but poisonous, Japanese lacquer. 


A NATURALIST’S PARADISE 39 


But we were almost forgetting the palms (some over 
100 feet high) and palmettos, and the Caribbean pines. 
Most remarkable of all is the living fossil called Zamia, 
a descendant of the giant cycads of the Carboniferous 
age. The pollen from the male plant, borne by the wind, 
settles on the naked ovules of the female plant, and sends 
out a pollen tube. In this, as in other Cycads, there are 
produced relatively large motile spermatozoa like those 
of animals and of non-flowering plants such as ferns. 
“The ovules of Zamia floridana develop into beautiful 
orange-red fleshy fruits arranged about a central axis, 
like large grains of corn around a cob. These are at first 
covered by the peltate, triangular scales which bear them, 
but they fall off when fully ripe and form conspicuous 
bright-coloured heaps in the pine lands where they grow”’ 
—interesting jetsam of a vegetative tide that spent 
itself long since. 


The Struggle for Life 


From the impression of the abundance of plant life 
rises another, the impression of struggle. There is keen 
competition, seen in miniature in our hedgerows, for light 
and fresh air. The 


“jointed liana” roots in the ground, forming loops which 
trip up the unwary; “‘its opposite, arm-like branchlets, which 
terminate in tendrils, clasp the tree trunks as the plant makes 
its way up to the light. When it has established itself, and 
spread over the branches, the arms, no longer of use, break 
off at the shoulders and leave the vine hanging like a great 
rope usually at some distance from the trunk, causing the 
observer to wonder by what means it had reached its point 
of support. This plant covers the crown of a tree so thickly 
that its host is sometimes crushed under its weight.” 


There are many others—vines, zarzaparillas, a cassia 
bearing nicker nuts, a giant bean, and the sweet bamboo 


40 SCIENCE, OLD AND NEW 


briar, all illustrating in various ways the same endeavour. 
Strangest, perhaps, is the strangling fig, Ficus aurea, 
which starts, like the mistletoe, from a tiny seed dropped 
by a bird on the limb of a tree. It sends down threads 
which reach the ground and root. ‘‘They grow together 
wherever they touch one another, forming a meshwork 
about the trunk of the host which is slowly strangled to 
death. This may well be designated the snake tree, or 
constrictor, of the vegetable world.” It is interesting 
to notice that the extreme competition of the jointed 
liana and the strangling fig is apt to defeat itself by killing 
the supporting host. Mr. Safford’s fine pictures recall 
Stevenson’s Woodman: 


Thick round me in the teeming mud 

Brier and fern strove to the blood: 

The hooked liana in his gin 

Noosed his reluctant neighbour in: 

There the green murderer throve and spread, 
Upon his smothering victims fed, 

And wantoned on his climbing coil. 


It may seem that we were premature in saying ‘‘every 
prospect pleases,” but perhaps if there had not been this 
sort of woodland warfare in the cycad forests of the Car- 
boniferous age, there might not have been any flowers 
upon the earth to-day. 


Linkage of Lives 


It is pleasanter to think of the orchids on the trees, the 
highwater mark of the floral tide, such as the white- 
flowered spider orchid which exhales exquisite fragrance 
towards nightfall, and the chintz-flowered orchid which 
Hans Sloane compared in 1707 to patches of Dutch 
chintz, and a common one with yellowish-green flowers 
which blooms continuously throughout the greater part 


A NATURALIST’S PARADISE 41 


of the year. There are many other epiphytes, some of 
which hang down in beautiful moss-like festoons. The 
‘resurrection fern,” growing on the branches, shows an 
interesting adaptation, for it curls up its fronds in drought 
and uncurls them when the rains return. The bromeliads, 
also perched on the trees, have at the bases of their 
leaves little reservoirs in which water collects, making a 
sort of arboreal swamp in which tree-frogs and even 
dragonflies lay their eggs. This is our third impression, 
the endless intricacy of the interrelations by which one 
creature is linked to another in the web of life. 

The abundance of water-plants in the slough allows 
of a vast population of small water animals, crustaceans, 
insect larvee, molluscs, and all the rest; and these afford 
food for higher incarnations in fishes, reptiles, and birds. 
‘One of the most common occurrences is to see a magnifi- 
cent osprey swoop down on what appears a grassy prairie 
and rise with a good-sized fish in its talons.’’ Similarly, 
the great marsh snail is the staple food of the Everglade 
kite, and the crawfishes support the blue heron and the 
white ibis. The welter of humbler creatures makes a higher 
grade life possible, and the animate world is run on a plan 
of successive incarnations. This, again, is an impression 
of linkages. 


Abundance of Animal Life 


The wealth of insect-life is baffling—butterflies like the 
unpalatable zebra-marked Heliconius which insectivorous 
birds leave unmolested, day-flying wasp-moths with 
transparent windows in their dainty wings, lustrous 
jewel-wasps which lay their eggs in the decanter-like 
earthen nests of the potter-wasps, leaf-cutting bees, 
carpenter ants, a lichen-like mantis with bad habits, and, 
delightful to watch, graceful dragonflies, ‘‘like squadrons 
of miniature airplanes, waging incessant war upon the 


42 SCIENCE, OLD AND NEW 


besieging mosquitoes.’’ Very curious are the opalescent 
ground-pearls found in quantities in the black soil of the 
wood. Children string them into necklaces. They are 
the exudations of certain scale-insects or Coccide, and 
the creature may be found inside. Many insects mean 
many spiders, some of which make us dumb by their 
diablerie. The female Golden Miranda, nearly an inch 
long, makes a web about two feet in diameter among the 
marsh grass; the male is only a quarter of an inch long and 
requires to be very circumspect. Another paradise spider 
is Nephila clavipes, whose golden-yellow silk, woven into 
bed curtains, was exhibited as a curio at the Paris Exhibi- 
tion. She has an insignificant bridegroom whose honey- 
moon often comes to a premature end. The young ones 
are cannibalistic from birth. Our fourth impression from 
Paradise Key is of the still unfathomed subtlety of animal 
behaviour. 


Higher Animals 


There are many fishes in the adjacent waters, from tiny 
top minnows, which devour the larve of mosquitoes, to 
the big bony pike or alligator gar (up to seven feet), 
famous for its voracity and for its beautiful armour of 
enamelled rhomboid scales. There is another very inter- 
esting fish of ancient pedigree, another living fossil, the 
well-known Amia, ‘‘one of the hardest fighters that ever 
took the hook.” Amia is famous for gameness and 
voracity; but look at the other side, turning from hunger 
to love—‘‘the male builds the nest and guards it after 
the eggs are laid; he is a good father, even accompanying 
and protecting the schools of young after they leave the 
nest.’ Why should it be thought that this aspect of the 
struggle for existence is any less a matter of fact than the 
cannibalism of the spiderlings? 

Passing reluctantly over the tree-toads (one of them 


A NATURALIST’S PARADISE 43 


*‘scarcely bigger than a dime’’), the Floridan bull-frog 
which grunts like a pig, the turtles and terrapins, the 
alligator and the crocodile (both of them timid creatures, 
very much afraid of man), the so-called chameleon 
famous for its quick changes, and a variety of friendly and 
unfriendly snakes, we reach the climax of the whole—the 
birds and the mammals. The latter include the Floridan 
opossum, various rats and mice, a lynx, an otter, a raccoon, 
and various others; while in the waters not far off there is 
the manatee, called a sea-cow by some and a mermaid by 
others (so much depends on the point of view!), one of the 
two representatives of the old-fashioned order of Sirenia. 
The birds are far more numerous and more fascinating— 
the Everglade kite, the osprey, the uncanny snake-bird 
which dives from the trees after fishes, the American 
bittern, stately “‘lady of the waters,” the black-crowned 
and yellow-crowned night-herons (‘‘whose day begins 
after sunset’’), the white ibis and the roseate spoonbill, 
one of the most beautiful of birds, delightfully social in its 
ways. This masterpiece of gracefulness and fine colour- 
ing has become very rare in North America, doomed by 
the very beauty of its plumage. It is to be hoped that it 
will be saved from extermination in the sanctuary of 
Paradise Key, for it is the climax of our final impression, 
that of the Ascent of Life. Wewere so much charmed by 
Mr. Safford’s report that we have ventured to try to hand 
on these five impressions which are dominant in our mind, 
but we know that they cannot have the convincingness of 
the original detailed picture. Yet we do not need to visit 
the Floridan Everglades to verify these fundamentals— 
the abundance of life, the struggle for existence, the in- 
tricacy of vital linkages, the subtlety of animal behaviour, 
and the general ascent of organic evolution. 









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VI 


SEA SNAKES AND SEA SERPENTS 


45 





SEA SNAKES AND SEA SERPENTS 


ONCE upon a time, millions of years ago, there were 
genuine sea serpents; and we are not denying that there 
may be some living to-day. But people who talk about 
them are looked queerly at, so let us keep to the facts as 
long as we can. We are alluding to the Pythonomorphs 
that lived in the Cretaceous seas. As the greatest living 
paleontologist in Britain says—‘‘They must have had a 
very wide distribution, remains being met with in Europe, 
North and South America, and New Zealand.’ They 
belonged to the Lizard-Snake alliance, but they were sea 
serpents; and they flourished at a time when modern 
lizards and snakes had not been evolved. One must re- 
member that in these distant Cretaceous days the ruling 
class was still reptilian; the future ruling classes, the birds 
and the mammals, were still at the level of ‘‘cranks.’’ We 
fancy, however, that these incipient creatures, of higher 
cerebral degree, gave the dominant reptiles a good deal of 
anxiety. We are attracted by the suggestion that the 
“‘death-feigning”’ or ‘‘playing ‘possum’”’ of various mam- 
mals may have historical reference to the time when 
the only chance of the pigmy incipient mammals in 
the clutch of the overwhelmingly big reptiles was to lie 
low, and pretend to be dead. For, while we cannot 
be sure about the extinct Dinosaurs, we know that 
many modern reptiles insist on catching living booty 
for themselves. 


47 


48 SCIENCE, OLD AND NEW 


Extinct ‘‘“Sea Serpents” 


The Pythonomorphs differed from true snakes in having 
paddle-like limbs, but they were like true snakes in the 
elongated body (up to 45 feet), the large number of verte- 
bre (up to 130), the loose union of the two halves of the 
lower jaw in front—an adaptation which allows of swallow- 
ing relatively large victims. ‘Towards the same end there 
is a remarkable hinge half-way along the lower jaw on each 
side, which must have allowed a bowing out in a curve 
when the booty was ‘‘too big for the mouth.”’ The back- 
ward curving of the teeth is plainly suited for fish-catching. 
One of the best known of the Pythonomorphs is Mosasau- 
rus, called after the Meuse near which its fossil remains 
were first found. Perhaps we are wrong in applying 
the name ‘‘sea serpent’? to these Pythonomorphs or 
Mosasaurus, for we do not dare to say much more than that 
they belonged to the lizard-snake stock. We must not 
make too much of the elongated eel-like shape, for it is 
said to have arisen 44 different times in the evolution of 
Vertebrates. The Pythonomorphs left the land early in 
the Cretaceous; they were terrors of the sea for perhaps 
3,000,000 years; and then towards the end of the geologi- 
cal middle ages (Mesozoic) they suddenly disappeared. 


Modern Sea Snakes 


Now let us turn to the modern sea snakes (Hydrophi- 
dz), a very interesting family, widely represented from 
the Persian Gulf to Australia. There are a lot of them; 
sometimes seen a hundred miles from land, very poison- 
ous fish-eaters. Like the Pythonomorphs they have sprung 
from a terrestrial ancestry, and they show some intelli- 
gible adaptations to marine life. Thus the tail is flattened 
from side to side, making a better paddle; and the same 
is sometimes true of the posterior body. It may be ex- 


SEA SNAKES AND SEA SERPENTS 49 


plained that the tail of a snake is usually short; it is the 
region behind the end of the food-canal and its vertebre 
have no ribs. The single lung of the sea snake is very 
long, reaching right to the end of the food-canal, and this 
must make it easier to remain a long time under water; 
for it must be kept in mind that the inspiration and ex- 
piration must take place at the surface. 

An ordinary terrestrial snake has along its ventral sur- 
face a single row of large scales, which grip the roughnesses 
of the ground. These are replaced by small scales in the 
sea snakes, except in one case, the gentle but poisonous 
Platurus, which keeps to the ancestral type and often 
ventures ashore. An ordinary terrestrial snake is continu- 
ally feeling its way and testing things with its mobile 
sensitive tongue; it is interesting to find that in the sea 
snakes the tongue is very short. These differences as 
to scales and tongue are intelligible when we think of the 
aquatic life, but it is not so easy to understand why the 
sea snakes have small eyes, or why they moult the outer 
covering of the skin in rags and tatters, instead of in a 
continuous slough as ordinary snakes do. Perhaps a 
peeling off en bloc would be difficult in the open water; 
perhaps it would leave the animal imperilled. 

The sea snakes are elusive and irascible reptiles. They 
are as awkward on land as they are agile in the sea, and 
when they are captured they lash about wildly, biting even 
at their own body. They seem to be half-blinded by the 
glare. Their bite is very dangerous, and may be rapidly 
fatal to man. A naturalist writes of an experience in 
Manila Bay: 


We were anchored about three miles from the land, in 
water twenty feet deep. To while away the time we fished, 
but either our tackle was too clumsy or our bait unsuitable, 
for we had not even a bite all day. As night came on we kept 
our lines in the water merely for experiment’s sake, without 
the remotest idea of catching anything. The sea was calm, 


50 SCIENCE, OLD AND NEW 


and the darkness intense. Between 9 and 10 P.M. we caught 
six water snakes on hooks of large size, baited with salt pork, 
and resting quietly on the bottom. They were of about the 
same size, three feet long, and very savage, snapping at every- 
thing within their range. 


One is not surprised to find that the sea snakes are 
viviparous, for the developing eggs would soon drown in 
the sea, and apart from bringing forth living young ones 
the only other practicable possibility is that the mothers 
should bury their eggs on the warm sandy shore as turtles 
do, or should lay them on land and brood over them. But 
true sea snakes, except the aberrant Platurus, never leave 
the water, though in some cases the mothers bring forth 
their young ones among the sea-shore rocks and guard 
them there for weeks. The case of Platurus reminds us 
of the important conclusion of Dr. G. A. Boulenger, that 
besides the true sea snakes or Hydrophide there are three 
other marine groups which have diverged independently 
from terrestrial ancestors. Why creatures so thoroughly 
terrestrial as snakes should take to the water at all is a 
difficult question. Perhaps there was over-crowding, 
perhaps there was over-persecution, perhaps the land be- 
came too arid even for snakes, perhaps there was gradual 
subsidence of the coast, perhaps the spirit of adventure 
moved certain types to explore a new kingdom. It is often 
good science to say ‘‘perhaps.”’ 


Sea Serpents 


But we wish, thirdly, to say a little about the sea 
serpents of modern times, of many cf which careful de- 
scriptions have been given. No one can doubt that many 
sober witnesses have seen the appearance of sea serpents. 
To what are these appearances due? We may, as it were, 
distinguish several species of sea serpent, and some are 
better species than others! There is an Indian file of 


SEA SNAKES AND SEA SERPENTS 51 


porpoises; a chain of sea-fowl flying low; an immense 
length of kelp slowly drifting; a couple of 30-feet long 
basking sharks keeping time as they swim, one behind the 
other; an immense jellyfish with its frilled lips trailing 
behind for over 30 feet; the silvery oar-fish, 20 feet long, 
lurching in some agony out of the water; a pair of huge 
sea-lions or elephant-seals playing in the waves; or some 
huge cuttlefish, which with its long arms may reach a 
length of 60 feet. These are some of the species of sea 
serpents, but there are two considerations which lead 
us to refrain from dogmatically interpreting every sea 
serpent as a misinterpretation! First, there are several 
careful descriptions which cannot be readily referred to 
any of the species we have just noticed. Second, it must 
be remembered that sailors have good sight and are very 
familiar with many of the appearances noticed above. 
They declare that the sea serpent they saw was none of 
these! Surely it is too soon to suppose that we have dis- 
covered all the creatures of the sea. We are not aware, 
for instance, that anyone has seen the cuttlefish to which 
there belonged the scale-covered chunk exhibited by the 
late Prince of Monaco at the Paris Exhibition. 


















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VII 


THE ENCHANTED _.WOOD 


53 





THE ENCHANTED WOOD 


REMEMBERING what Wordsworth has said as to the edu- 
cative value of a vernal wood, we recently visited a sum- 
mer wood—by the shore of Windermere. Perhaps it is the 
season that makes the difference, but we have not found 
any fulfilment of the poet’s promise of increased wisdom. 
Or it may be that the fault is ours, or the wood’s? For 
there is great diversity in the character of woods, as every- 
one knows. The pine forest is stern, like an army before 
battle; the beech wood is kindly, with squirrels scampering 
about, and the rustle of the thick carpet of strewn leaves 
is pleasant under foot; the birch copse in the Scottish 
Highlands is full of delicate fancies, and at every turn a 
right of way to fairyland. But the wood we tried to make 
friends with, and could not, was another kind of wood, a 
sheltered wood, a Circean wood. It is like a garden en- 
closed, screened from the winds that prune, with a hot- 
house mildness, with an almost tropical luxuriance. We 
have called it Circean, partly because of the abundance of 
Enchanter’s Nightshade (Circa), and partly because we 
were glad to be out of it—symbolic as it seemed of the 
sheltered life of ease. 

Seen from a distance—we wish to be quite fair—the 
wood is very beautiful. It slopes up the hillside lke ter- 
races of thatched cottages, a pleasantly uneven and 
variegated verdure. It is what one calls a mixed, self- 


55 


506 SCIENCE, OLD AND NEW 


sown wood, with oak and elm, hazel and alder, sycamore 
and ash, rowan and wild cherry—but hardly a decent 
tree amongst them. It is not that they are young; what 
is wrong is that they have not grown up. Tall, lanky 
weaklings, struggling up to the light, without girth, with- 
out grit. Some of them have become the dead or dying 
props of ivy. In other cases we saw sapling and honey- 
suckle sharing a common doom. Seedlings everywhere, 
delicate beauties without strength, crowding one another, 
shadowing one another, dwarfing one another. It is like 
the jungle in Stevenson’s Woodman. Beauty, of course, 
and an absence of disease, apart from parasitic moulds 
and rusts, gall flies and leaf mites, but what a lack of 
vigour! So many of the leaves are etiolated, which does 
not mean withered; so many of the stems are smothered 
in lichen. Not only are there mosses spreading up the 
branches, but polypody ferns as well, perched high above 
the ground. Everything speaks of the struggle for air 
and light; almost everything confesses failure. It is a 
depressing enchanted wood. 

The undergrowth is dense; there is no brown earth to be 
seen. But the dominant impression is of much, not of 
many. The poverty of the flora is extraordinary, in the 
sense that only a few different kinds are represented. 
Only those have survived that are able to endure the deep 
shade. There were stretches of blaeberry bushes without 
any flower or fruit, ramping brambles that never have 
more than blossoms, and prostrate honeysuckle and ivy 
that seem to remain quite vegetative. Here and there 
a mass of woodruff without any fragrance, a bed of dog’s 
mercury, a clump of wood sanicle with beautiful glossy 
leaves, clusters of wood sorrel, and everywhere enchanter’s 
nightshade; but that is almost all. In other words, there 
is a sparse flora of shade plants—beautiful, no doubt, and 
luxuriant, but within a very narrow range. Quarter of a 
mile away, the meadow is a blaze of colour even in late 


THE ENCHANTED WOOD 57 


August—purple centauries, ruby-coloured salad burnet, 
golden rods, horse gowans, sage, agrimony, and a dozen 
more, but in this enchanted wood there is hardly a touch 
of any colour but green. Very characteristic are little 
glades of graceful cow-wheat with pale yellow pendent blos- 
soms, sometimes almost white, but we could not find even 
common weeds like wound-wort or herb-Robert—no, not 
even a thistle. There was not a single flower that could 
be called a flame; nothing got beyond smouldering. 
There was no mistaking the inhibition of the sheltered 
life. We were in a crowd of beautiful invalids, and even 
the leaves were often dwarfish. 

The tangled green curtains shut out the sun and the 
breeze; the rain drops from the forenoon’s shower still 
hung from the leaf tips; the atmosphere was like that of a 
hot-house; and if we had been told that the percentage 
of oxygen was under the average we should not have been 
surprised. At first we rather liked the dense shade and 
the absolute quiet—without even a hint of the procession 
of char-a-bancs not very far away—but it gradually be- 
came sinister. It was like being in a cave. There were 
exquisitely beautiful old silver lichen cups and mosses 
with spore cases of gold, and no doubt there was an abun- 
dant cryptozoic life of microscopic animals, but beyond 
pin-point midges and an occasional slug on the uppermost 
branch of a thorn, there was no indication of the delight- 
ful creatures that usually ‘‘glide in rushes and rubble of 
woody wreck.” How one would have welcomed a toad 
or even a brisk centipede! We did not expect an orchestra 
of birds at the end of August, but we only heard one in the 
wood—a churring fern owl, and, of course, with his gar- 
ment of invisibility, he was not to be seen. Away in the 
distance we heard a barn owl and a moaning dove, but 
neither of them belonged to the enchanted wood. Here 
and there we saw that spiders had been at work, but it was 
part of the picture that what they had made were rough 


58 SCIENCE, OLD AND NEW 


and ready snares rather than true webs. What they had 
caught were winged green-flies or Aphides. 

When we came to the far end of the wood there was a 
rustic bridge and the only joyous thing we had seen— 
a stream that made a silver staircase of broad low steps, 
stretching up and up through an endless pergola of green 
boughs. It was illumined to the outer side, and dark 
towards Circe’s wood. We hurried across the bridge, 
glad to be away from the sheltered life of ease, back in 
an open and strenuous world where there is less luxuri- 
ance and more virility. 


VIll 


CAVE ANIMALS 


59 





CAVE ANIMALS 


THE most highly evolved tenants of caves are bats, and 
their choice of a dark home is congruent with their twilight 
activities. They do not like the light of day; they have 
made a speciality of the dusk. Some of the caves of the 
East are peopled by thousands of bats, and travellers tell 
us how kites and falcons congregate every evening outside 
a cliff-cave and await the sortie. In a brown torrent, ten 
feet deep and ten feet wide, the bats rush forth, and it is 
easy for the birds of prey to secure abundant booty. 
Yet the nightly thinning does not seem to make any 
appreciable difference in the number of the bats. They 
are legion. 


Permanent and Partial Troglodytes 


But in thinking of bats as cave-dwellers, we must 
remember that, weather permitting, they sally forth every 
night, just as otters may, or hedgehogs from the bole of 
the old tree. The bats are not like the permanent tenants 
which are found in moist or wet caves, such as the Mam- 
moth Cave of Kentucky, or the Adelsberg Caves not far 
from Trieste. Let us take the Proteus of the Adelsberg 
Caves as a good example of a true troglodyte. This 
quaint creature is a newt about ten inches long, of a wan 
white colour, slightly tinted by the red blood which makes 
the three pairs of protruding gills a vivid carmine. The 

61 


62 SCIENCE, OLD AND NEW 


eyes are degenerate and quite hidden below the skin, so it 
must be by smell or by detecting movements in the water 
that Proteus secures the small animals on which it feeds 
somewhat ascetically. The caves are quite dark; the water 
of the stream that traverses them for miles has a low tem- 
perature of about 10° C.; but Proteus seems to thrive. 
Experiments show that it is put about by the light of a 
candle, and we must regard it as an animal with a con- 
stitutional antipathy to illumination—some innate deli- 
cacy, perhaps, which has led it to seek out a dark asylum. 
Very remarkable, however, is the fact that experimental 
exposure to light results in the development of grey 
patches on the skin, and eventually in the appearance of 
dark pigment all over the body. It would have seemed 
so natural to conclude that the pigment-producing quality 
had quite dropped out of the inheritance of this cave- 
dweller, and yet experiment proves that it has not. 
Given the fit and proper nurture, the hereditary na- 
ture expresses itself; the white newt becomes black. We 
should be careful at a higher level not to conclude too 
hastily that dwellers in darkness have quite lost a quality, 
though they show as little of it as the Proteus in its caves 
shows of pigment. A near relative of Proteus, called 
Typhlomolge, occurs in subterranean caves in Texas—a 
fine instance of parallelism in evolution, for the two 
animals doubtless arose independently from an ancestor 
like the North American Necturus. 


Is Cave-Blindness Due to Disuse? 


We cannot do more than nibble at the familiar problem 
—did living in darkness make these cave-newts blind and 
wan, or did they seek out an asylum in darkness because of 
innate variations in the direction of weak eyes and weak 
pigmentation? Goldfishes kept in absolute darkness for 
three years become totally blind, losing the rods and cones 


CAVE ANIMALS a 


of the retina. There is no doubt as to the individual 
modifications—dints due to peculiarities of nurture; but 
we do not know, though we ought to know, whether the 
offspring of the blind goldfishes were the worse of what 
happened to their parents. When small freshwater 
crustaceans, such as ‘‘screws’’ (Gammarus), and ‘‘water- 
slaters’’ (Asellus), are kept for a long time in darkness 
they become very pale, and if the experiment is continued 
for years, generations are born with almost no pigment. 
But this may simply mean, as in the case of Proteus, that 
the stimulus required for pigment-production is absent 
during the development of the individuals. If translucent 
individuals are taken from the caves and kept in the light, 
they become brownish. One experimenter who exposed 
young stages of Proteus to the light, declares that the eyes 
advanced far beyond their usual state of arrested develop- 
ment. It is obviously very difficult to discriminate 
between -peculiarities imprinted on individuals and 
peculiarities due to hereditary defect; and, likewise, to 
decide between the neo-Darwinian theory that ascribes 
the hereditary defect to a germinal weakness, and the 
neo-Lamarckian theory that ascribes the hereditary defect 
to the cumulative results of disuse and darkness. It is 
quite possible, moreover, that a hereditary defect may be 
exaggerated in the individual by the peculiarities of cave 
nurture. But this is a King Charles’s head among 
biologists. 

Very interesting is Professor Doflein’s case of a tiny 
Japanese crab (Cyclodorippe) which occurs in two very 
different habitats—shallow water and deep water. In the 
shallow-water variety the eyes are well developed and 
darkly pigmented; in the deep-sea variety the eyes of the 
adult are very rudimentary, though those of the larve, 
which the mother carries about with her, show all the 
essential parts and are dark in colour. Here we have to 
deal with a seeing variety and an almost blind variety of 


64 SCIENCE, OLD AND NEW 


the same species. But it would be rash to conclude that 
it is all a question of habitat; there is probably a con- 
stitutional dichotomy that leads the two sets of variants 
to different haunts. 

Another very instructive case is that of a blind and 
colourless fish, Typhlogobius, which lives on the Califor- 
nian shore. This seems almost a contradiction in terms 
till we find that the fish keeps exclusively to dark places 
under shelves of rock—sea-caves in fact—where it fixes 
itself by means of its pelvic fins united into a sucker. 


Caves as Asylums 


Among the true cave-animals we include representatives 
of newts and salamanders, fishes, snails, spiders, insects, 
centipedes, crustaceans, worms and humbler creatures. 
They tend to be translucent or dull in colouring; they 
often show arrested or degenerate eyes, but by no means 
always; they have usually a fine sense of touch; and they 
seem to be able to thrive on very little food. It is a 
strange company, impoverished by being shut off from the 
sun’s energy. More facts are necessary before we can 
give a secure interpretation of the origin of cavernicolous 
animals and of the peculiarities they exhibit, but we 
incline to the view that the majority are handicapped by 
some constitutional infirmity, such as inability to keep a 
place in the sun, and that they have found in the caves an 
asylum. They are not weak because they are troglodytes; 
they became troglodytes because they were weak. 


TeX 


HERALDS OF SPRING 


65 


* 


Pl. 
? \ 





HERALDS OF SPRING 


For many millions of years there was no living voice to 
be heard on the earth. The only sounds were inanimate, 
like those of wind and wave, thunder and torrent. Unless 
we count the instrumental volubility of certain insects, 
like grasshoppers and crickets, which produce sound by 
moving one part of the body very quickly on another part, 
the first voice of life is to the credit of amphibians 
probably towards the end of the Old Red Sandstone epoch. 
For amphibians were the first animals to have vocal cords 
—tightly stretched membranes which give forth sounds 
when the out-breathed air passes rapidly over them. 





Croaking of Frogs 


It is interesting that the first animals to have a voice 
should also be among the first animals to break the silence 
of winter. For frogs are among the earliest heralds of the 
Spring. There are, indeed, heralds of the Spring who cut 
a finer figure than do the frogs as they emerge from the 
mud by the side of the pond, or from secluded holes where 
they have spent the winter, but there are few that we can 
trust more confidently. When a lot of them have begun 
to croak we may be fairly certain that it will not again 
be very cold, that the winter is over and gone. ‘There is 
many a snowstorm after the cawing of the rooks—false 
prophets of Spring—but there is rarely one after the 

67 


68 SCIENCE, OLD AND NEW 


croaking of the frogs. All the winter through they have 
been lying half-alive, mouth shut, nose shut, eyes shut, 
breathing through their skin in a way higher animals have 
quite lost, and with their hearts beating feebly. Now 
they are awake again, and, in spite of their long fast, their 
slowly moving thoughts are all for love and none for 
hunger. The males call to their mates, who are weakly 
but distinctly responsive; the pairing instinct must be 
satisfied first, meals will come later. Love is stronger than 
hunger. 

To our ears there is nothing very attractive in the 
frog’s croaking, but it is not meant for our ears. Itisa 
sex-call, and that is the primary significance of the voice. 


Other Heralds 


As we sat in the sun by the riverside we heard many her- 
alds of the Spring. Handsome oyster-catchers with ruddy- 
orange bill and feet flew up and down in parties of three 
or four uttering shrill screams. They must cover scores 
and scores of miles in a day. The lapwings were flying 
very high and calling to one another, half plaintively, 
half mischievously. ‘There was a voice also in the whirr 
of their wings as they swooped past us at top speed. 
There were redshanks with a beautiful trill in their clear 
whistle, and the curlews that had come to the river from 
the sea had a new music in their call. Little titmice were 
playing hide-and-seek among the branches of the larch- 
trees and calling to one another with sibilant incisiveness. 
There were jackdaws, too, in high spirits, besides thrushes 
and blackbirds, chaffinches and robin-redbreasts, and 
more besides—all calling, ‘‘Here I am, here; come hither 
love—here.”’ 

Tt seemed almost a bathos when some frogs gave voice 
from a marshy place close by the river, but one must hear 
with more than the hearing of the ear if one is to under- 


HERALDS OF SPRING 69 


stand aright. This croaking—why, it is a persistent echo 
of the first voice, and as such eloquent. If frogs had not 
croaked, could man have become man? Let us linger 
over the Natural History of the voice. 


Drummer-fishes 


As we have seen, a true voice began with backboned 
animals, and to all intents and purposes with amphi- 
bians, which made their appearance at the end of the 
Devonian Epoch. But fishes are not altogether mute. 
In the case of the drum-fishes there is a voluntary pro- 
duction of sound, most marked at the breeding season. 
The sound seems to be due, not to a grinding together of 
pharynx teeth, as was formerly supposed, but to a rapid 
and regular contraction of a special muscle on each side of 
the middle line of the ventral surface. The contractions 
and relaxations of this muscle rhythmically reduce and 
increase the size of the body-cavity, and there is a ten- 
don running up to the swim-bladder which acts as a 
resonator, adding considerably to the carrying power of 
the sound. In some kinds of drummers there is drum- 
ming in both sexes, but there are other kinds in which it is 
the male’s prerogative. In both sets of cases the drum- 
ming is probably a love-signal. 


The Amphibian Voice 


Among amphibians, in the frogs and toads there is the 
first true voice. That is to say, the air from the lungs 
passes rapidly between two taut membranes (vocal cords) 
which vibrate and produce sounds. In the Surinam toad 
the vocal cords are represented by two rods of gristle, 
which also vibrate, reminding one of a tuning-fork. 


70 SCIENCE, OLD AND NEW 


It is part of the tactics of evolution to make an ap- 
parently novel thing out of what is really very old. ‘“New 
lamps for old’”’ is the ancient magician’s cry. So the 
frog’s lungs correspond to the swim-bladder or air-bladder 
of the fish and the parts of the gristly framework of the 
larynx correspond to gill-arches. What the vocal cords, 
stretched within the larynx, correspond to, we do not 
know. Perhaps they are distinct novelties. For while 
there is a conservatism in evolution, using the old for 
something new, there is also creativeness, originating new 
things of which we can give no more account than we can 
of genius. ‘‘God said: Let Newton be, and there was 
light.”” The firsts Amphibian to give voice was another 
genius. The carrying power of the sound is often increased 
by the development of a resonator, the so-called croaking 
sac. The deep bass call of the American Bull Frog is 
said to be audible at a distance of a mile—measured on 
the spot. The croaking sac is an expansion of the floor 
or sides of the mouth, single and median, or paired and 
lateral. In many male frogs the croaking sacs can be 
protruded like big soap-bubbles from the corners of the 
mouth. In the tree-frog the inflated resonator may be 
larger than the head. The croaking-sacs are restricted 
to the males, and, as regards the voice itself, the females 
are either dumb or weakly responsive. 

The noise that male frogs can make is familiar to those 
who live near marshes. It was likened by Aristophanes 
to ‘“‘brek-a-brek-brek-brex-kaka-brex,’’ and it must be 
granted a distinct specificity—each amphibian has its 
own particular love-call, its own and no other’s. There 
is great diversity—croaking, quacking, trilling, ringing, 
chirping, howling, and caterwauling. Batrachologists 
can tell different kinds of frogs and toads by the voice. 
Its efficacy in summoning the females is well known. In 
newts and salamanders, unlike frogs and toads, there is 
little or no voice. 


HERALDS OF SPRING 71 


The Reptilian Voice 


Reptiles, though higher than amphibians, are less vocal. 
some of them have vocal cords that vibrate when the out- 
breathed air passes rapidly over them. In crocodiles 
there do not seem to be any vocal cords, but a sound is 
made by the air passing through the narrowed glottis 
(the opening to the windpipe), and below this there lies a 
resonating sac. Some crocodiles bury the eggs deeply 
in sand and mould, and when the young ones are ready 
to be hatched they pipe from within the egg. When the 
mother hears them she unearths them, otherwise they 
might be buried alive. This is an interesting case 
because it shows us the broadening of the use of the 
voice; it has become a child’s cry. 

Some lizards chirp; the monitors hiss; chameleons hiss 
and grunt. Perhaps these are deterrent sounds—another 
use of the voice. This is probably the meaning of the 
serpent’s single fearsome word. ‘The rattle at the end of 
the rattlesnake’s trail, rapidly vibrated when the animal 
is excited, is an instrument made of a series of hollow 
horny tail-sheaths which remain attached at a sloughing. 
It is rattled with such rapidity that a whistling sound 
results, and this may be useful in driving off large animals, 
like peccaries, on which the snake might have to waste its 
poison. For the rattlesnake has no hiss. 

The same kind of instrumental voice is illustrated by 
the males of most terrapins, which produce a clear note by 
rubbing a patch of tubercles on one leg against a similar 
patch on the other leg. Some of the climbing lizards or 
geckos produce similar musical notes, in both sexes, by 
friction between the scaly rings on the tail. But a true 
reptilian voice may be heard when the male tortoise wakes 
up at the breeding season; and some may have had the 
good fortune to hear the hoarse bellow of the male giant- 
tortoises of the Galapagos Islands. 


72 SCIENCE, OLD AND NEW 


The Voice Comes to Its Own 


In birds and mammals the voice comes to its own, and 
in both we have to do with vocal cords the tension of which 
can be altered. But there is this great difference: that 
the seat of the voice in mammals is in the larynx at the 
top of the windpipe, whereas in birds it is in a new struc- 
ture, the song-box or syrinx, situated at the base of the 
windpipe, where it divides into two bronchial tubes going 
to the lungs. Matters have become much more compli- 
cated, thus in a singing-bird there is the bony framework 
of the song-box, the internal vibrating membranes and 
folds, and a number of special muscles—up to seven pairs 
of them. The apparatus is usually simpler in the females, 
for singing is the cock-bird’s art. In various birds, like 
the ducks, and in various mammals, like the howling 
monkeys, the vocal apparatus is enhanced by the addition 
of a powerful resonator. 

But the most important fact of all is that while the 
voice remains in birds and mammals an expression and a 
provocation of love, its use has greatly broadened. It 
may be a parental call, a danger-signal, a filial cry, an 
appeal to kin, a means of conveying information, an 
instrument of social integration, and—eventually—a 
medium for expressing or concealing thoughts! 


xX 


A SOCIETY SECRET 


73 





A SOCIETY SECRET 


AMONG ants, bees, and wasps there is often vicarious 
parenthood. The ‘‘workers’”’ who take solicitous care of 
the young are not themselves normally mothers; they are 
females who remain, except in unusual cases, virgin and 
sterile. But as they are incomparable nurses, it has been 
generally supposed that they act as they do because of an 
engrained maternal instinct established in the history of 
their race long before there was any worker caste. In 
this view there is probably more than a grain of truth, 
though it should be remembered that the workers among 
Termites or White Ants are of both sexes. But the widely 
accepted view would obviously be easier to hold if we 
knew of any immediate reason—apart from that of racial 
welfare—why the parental care exhibited by the non- 
reproductive workers should continue so strong. That 
reason seems now to have been discovered. 

The first hint of the reason was disclosed by Dr. Rou- 
baud, whose studies of some tropical wasps showed that 
there is an interesting give and take between the nurse- 
wasps and the larve. The nurses feed the larve un- 
remittingly, yet not without immediate reward, for they 
get from the larve drops of an elixir of which they are 
extraordinarily fond. The vibrations of the nurse’s wings 
serve as the signal which prompts the larva to. protrude its 
head for food, offering in exchange the delectable drop. 
A corroboration of this reason for the workers’ devotion is 


75 


76 SCIENCE, OLD AND NEW 


given by Prof. W. M. Wheeler, who shows that a similar 
kind of ‘‘symbiosis” holds for some kinds of ants, and 
probably lies at the roots of the social habit. 


Danger of Biologism 


But before we summarise Prof. Wheeler’s story, we would 
suggest a caution, that the discovery of a physiological 
factor does not disprove, what is so difficult to prove, 
the reality of a psychological factor. In their constant 
routine of feeding, licking, transporting and defending 
the young, the worker-ants exhibit extraordinary persist- 
ence, and it is a tenable position that the expression of the 
inborn ready-made capacity which we call instinctive, is 
suffused with awareness and backed by endeavour. In 
many cases of instinctive behaviour this assumption seems 
almost necessary if we are not to make the whole business 
magical. But the via media is difficult. On the one hand 
we have grown away from the old view that everything 
is cleared up by invoking ‘“‘the compelling power of 
affection’’; on the other hand we feel that a physiological 
urge is a poor substitute for mind. It was only part of the - 
truth that Swammerdam stated in the Biblia Nature 
(1737)—‘‘with incredible affection” (he used the Greek 
word ‘‘Storge’’) ‘‘and care the ants bring up their vermi- 
cules and omit not the least thing appertaining to their 
education and nurture’’; but it was a glimpse of a truth 
without which, as it seems to us, all is darkness. 


The Larva’s Give and Take 


The mistake has been made of taking for granted that 
the sluggish legless larva or grub is only a passive recipient 
of the food the workers supply. In many cases it is far 
otherwise. Prof. Wheeler finds that in some of the Pone- 
rine ants the workers turn the larve on to their broad 


As SOCIETY I SECREL 77 


backs with their head and neck folded over on to the 
concave ventral surface, ‘‘which serves as a table or trough 
on which the food is placed.’’ This food usually consists 
of fragments of insects which the workers have dismem- 
bered, and on these the grub discharges from its salivary 
glands an abundant digestive juice. This dissolves the 
food on the table, so that the grub can swallow and 
assimilate it, but—and here is the point—it also supplies 
a pleasant draught for the nurse. It is well known that 
the common tropical tailor-ants use the young larvee of the 
nest to supply from their silk glands the silk threads with 
which they weave a web among the leaves; what is now 
made clear is that the large salivary glands of many other 
ant-larve supply refreshment and food to their nurses. 
In some larve that have soft blunt jaws and are fed with 
drops of regurgitated liquid food, there is no external 
secretion of salivary juice. But some of them have deli- 
cate tubercles or a tentacle-like outgrowth containing 
coagulated liquid which seems to be exuded and licked 
up by the workers when they are feeding and attending to 
their charges. 


Exudations Extraordinary 


The exudate, which is prepared in what is called the 
“fatty body”’ of the larva, is really blood rich in nutrient 
substances, and it probably filters through microscopic 
pores in the cuticle. That this is not unique we are 
reminded by the familiar experience of having a blister- 
beetle or a lady-bird discharge on our fingers, from parti- 
cular points on its legs, a strongly smelling liquid, which 
turns out to be blood-serum. But an exudate that has a 
repulsive and offensive function in the blister-beetle may 
have an attractive or nutrient function in certain ant- 
grubs. And again we may recall what Father Wasmann 
and others have told us of the attractive exudation that 


78 SCIENCE, OLD AND NEW 


comes from the blood-fluid and the fatty body, or from 
special skin-glands, in some of the little beetles which 
various ants keep as guests or pets. The exudation is 
sometimes distributed on special hairs, and from these it 
is easily licked up by the ants, or is simply evaporated, 
much in the same way as the secretion of sweat-glands is 
diffused and evaporated from the hairs in man’s armpit. 
There is a very interesting Tineid caterpillar, found in the 
tree nest of one of the Termites, which has seven long 
tapering appendages on each side of its body, from which 
there seems to be an evaporation of an exudate with a 
strong, probably alluring, odour. On Termites them- 
selves, as well as on their guests, there is often a marked 
development of exudation, and the amount of licking 
that the workers go in for is probably, as Holmgren says, 
“not the immediate expression of an altruistic philo- 
progenitive instinct,’ but rather an “‘exudate hunger.” 
Escherich reports that the workers in a Ceylonese termi- 
tary actually tear tiny strips off their bloated queen’s 
cuticle in order to get at the attractive exudate more 
readily. 


Weird Domestic Economy 


What Roubaud discovered in some primitive African 
wasps was a weird domestic economy. The larval secre- 
tion is enjoyed not only by the adult females who bring 
food, but by males and by newly-hatched females, who 
give the larve nothing. But they know how to turn on 
the tap by vibrating their wings and touching the grub’s 
lips. Roubaud suggested that the retention of the young 
females in the nest and the co-operative rearing of a large 
number of larve, crop after crop, may be traced back to 
the nutritive (or trophic) exploitation of the young. 
Social life, he said, is founded on ‘‘cecotrophobiosis.”” But 
as this term does not bring out the fact that in the main 


A SOCIETY SECRET 79 


the feeding of adults and larve is reciprocal, Professor 
Wheeler suggests the term ‘‘trophallaxis’’ (Greek 
‘“‘trophe,”’ nourishment, and ‘“‘allattein,’ to exchange). 
The nutritive relationship is clearly and characteristically 
co-operative or mutualistic. 


Nutritive Exchanges 


The thesis then is, that the social habit among certain 
ants and wasps is based on a nutritive exchange between 
adults and larve. That the symbiosis now exists is 
certain; that it is the outcome of an evolutionary process 
is suggested by an inclined plane of intermediate stages 
between merely storing food for the young and directly 
feeding the young, between feeding them right away and 
first preparing the food, between taking a share in the meal 
and finding the saliva of the larva agreeable, and so on. 
In attributing so fundamental a réle to nutritive exchange, 
Professor Wheeler sees the difficulty that the social honey- 
bees and humble-bees show no trace of it. For there does 
not seem to be any evidence that adult worker-bees ever 
feed on larval secretions. But this may be because social 
bees have evolved along vegetarian lines, living on nectar 
and pollen which are abundant and easily obtained. 
Another objection may be found in the fact that the ant- 
grubs turn into ant-pupe (the “‘ants’ eggs’’ of the shops), 
and while these yield neither liquid exudates nor secre- 
tions, they are carried about and defended by the workers 
just as carefully as were the larve. It appears, however, 
that the pupz have an attractive odour, and it is possible 
that their nurses have reminiscences! Moreover, pupe as 
well as larve 


represent so much potential or stored nutriment available 
for the adult ants when the food-supply in the environment 
of the colony runs very low or ceases entirely. Infanticide 


80 SCIENCE, OLD AND NEW 


and cannibalism then set in, with the result that the devouring 
of the young of all stages may keep the adult personnel of the 
colony alive till the trophic conditions of the environment 
improve. 


Other Nutritive Linkages 


Professor Wheeler’s theory opens up an expanding 
vista of great interest. A linkage that is, to begin with, a 
mutual relation between the mother-insect and her brood 
‘““has expanded with the growth of the colony like an ever- 
widening vortex.”’ The adult members of the colony 
may feed one another with regurgitated food or even with 
secretions; other species may be roped in to be fed and 
licked, alien races like the green-flies may be herded and 
‘‘milked’’ (Linneus’s vacce formicarum): and so the 
web of interrelations is woven—a web which becomes the 
subtle sieve of progressive new departures in socialisation. 
Another very interesting point is that the guests or pets 
kept by ants and termites often exhibit very remarkable 
and even bizarre shapes, suggestive of man’s fantails and 
bull-dogs. The probable explanation of this is that when 
sociality forms a biological unit larger than the individual 
or the family, and surviving in virtue of its qualities as a 
whole, there is permissible along certain lines (with 
restriction along others) a considerable latitude of in- 
dividual variation. Another line of interesting inquiry 
concerns the rewards of altruism. Even the exacting ante- 
natal partnership between the mammalian mother and her 
young, is normally one of health, of give and take, of 
symbiosis. For it has been shown that hormones or regu- 
lative chemical messengers pass not only from the mother 
to the unborn offspring, but from the offspring to the 
mother. And is there not in the characteristically mam- 
malian giving of milk a feeling of pleasure physiologically 
grounded—a pleasure which, as Bonnet suggested in his 
Contemplation de la Nature (1764) does something to 


APSOCIERY SECRET 81 


sustain the natural affection of the mother? And might 
one not work onwards to the fact that in his social inter- 
relations man finds one of his most rewarding methods of 
realising his self. Goethe said that Nature was always 
taking advantage of her children’s capacity for self-forget- 
fulness; but do we not, even in this story of trophallaxis, 
get a glimpse of a deeper truth, that the activities which 
last best are those which bring with them some immediate 
reward. 


Va 


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, ee , 
“ Tee PAA Fi i nie s se 
ee al : ‘4 oe eM ab a 


a 


vet ba so 
is ea aan 


Boa Ve 





eh 
ANTS AND PLANTS 








ANTS AND PLANTS 


It is well known that some ants collect seeds, like those 
of broom and gorse, and that they nibble at them, especi- 
ally at the ‘‘oil bodies.” They often lose their booty 
on their homeward journey, and, as they often use human 
tracks as their roads, this may account for the frequency 
with which bushes of broom and gorse grow by the sides 
of narrow footpaths on the moor. There is no doubt as to 
the seed-collecting, though it is not always certain what 
the ants make of what they gather. This seems to be the 
case, for instance, with the seeds of the cow-wheat, which 
are so like ‘‘ants’ eggs,” or, to be correct ants’ cocoons. 


Agricultural Ants 


The habit of collecting seeds points the way to storing, 
which is a subject by itself; it may also be the beginning 
of agriculture. But the old story of the agricultural ants 
of Texas, investigated by McCook, Lincecum, and others, 
is not beyond criticism. There is truth in it, but the inter- 
pretations of the earlier observers were a little too gener- 
ous. Round about their nest the agricultural ants make 
a clearing, often ten feet in diameter, and occasionally as 
much again. They are said to level the ground, and to 
leave patches of the grass Aristida, the seeds of which they 
collect and store and eat. Radiating from the clearing 
there are roads, which extend into the rank herbage, and 

85 


86 SCIENCE, OLD AND NEW 


are used by the ants continually on their food-collecting 
expeditions. Moreover, according to the old accounts, 
the ants are in the habit of sowing the ant-rice in the 
clearing and keeping the patches of their crop free 
from weeds. But Professor W. M. Wheeler has found 
nests of this agricultural ant without any Aristida grass in 
the vicinity; and, as to cases where dense patches grow 
near the nest, it is said that these are due to the ants’ 
habit of dumping down those Aristida seeds which have 
begun to sprout prematurely in the underground nest. 
It is a pity to spoil a good story, but the moral is that 
what looks like a well-thought-out scheme may not be so 
clever as it appears! 


Ants’ Flower Gardens 


One has read of “hanging gardens,” and they are to be 
seen as the handiwork of several kinds of ants in the 
region of the Amazons. They are made of earth, well 
kneaded and salivated, and they are attached to the 
branches of various trees and shrubs. Often they are 
the size of a man’s head, and they may be built fifteen feet 
from the ground or over fifty. The interior is a labyrinth 
of passages, where the busy workers run up and down. 
Sometimes there are underground dwellings as well. But 
where does the flower garden come in? 

The earthen nests are perhaps, just vast artificial 
extensions of the cavities of the plant in which the ants 
found their primary shelters when they took to arboreal 
life, but they have become something more, for, along 
with the building materials, there are included the seeds 
of many different kinds of flowering plants. These sprout 
and grow and blossom, and thus arises a flower garden. 
Naturally enough, the cultivated plants are for the most 
part local ‘‘epiphytes,”’ or ‘‘perched plants,” adapted for 
life on trees; but they have the advantage of being rooted 


ANTS AND PLANTS 87 


in the earth of the nest. Sometimes they grow so luxuri- 
antly that they make the nest too damp for the ants, 
but usually they shelter the nest from the torrential rains. 
It cannot be said that the whole matter is clear, but the 
flower gardens are roomy dwellings for the little people, 
and they are raised above the reach of the great floods. 
There is no evidence that the ants get any food from their 
gardens. 


Myrmecophily 


Thomas Belt, who was one of the early observers of the 
leaf-cutter ants, was greatly impressed by their destruc- 
tive powers. They defoliate certain trees persistently, 
and they must in this way sift the forest. But it wasa 
great pleasure to the naturalist of Nicaragua to discover 
that the leaf-cutters did not have it all their own way. 
He found that there were other ants that lived on the 
trees without doing them harm, and that these drove away 
the devasting leaf-cutters. This was independently dis- 
covered by Delpino, and so arose the theory of 
myrmecophily, to which the botanist Schimper made very 
important contributions. By a ‘‘myrmecophilous”’ (ant- 
loving) plant is meant one that affords food or shelter or 
both to a bodyguard of ants, which in turn drive off 
predatory and altogether destructive assailants, such as 
the leaf-cutters. 

some of the acacia trees of tropical America have 
large thorns (due to the transformation of stipules) at the 
base of their beautiful compound pinnate leaves, and in 
these thorns the bodyguard ants find shelter. But they 
get food as well as lodging, for the tips of the leaflets bear 
minute oval or pear-shaped bodies (Belt’s corpuscles), 
which are rich in protein and fat. They turn out to be 
transformed glands. They are easily detached, and they 
are much appreciated by the ants. When leaf-cutters 


88 SCIENCE, OLD AND NEW 


trespass on the preserves of the acacia ants, they get a hot 
reception, and are driven off. Thus myrmecophily 
m Payson 

Another much-studied case is that of the Imbauba, or 
Cecropia-tree, of Southern Brazil; a tall, slender tree with 
palmate leaves. It is tenanted by Aztec ants, who find 
their way through pre-formed weak spots into the archi- 
tectural cavities of the stem. Schimper said that, if the 
observer looks on quietly, he will see the Aztec ants 
running about looking after the aphides, or plant lice, 
whose honeydew they utilise, or nibbling at glandular 
white hairs, rich in protein and fat which grow at the base 
of the leaf-stalk. But if the observer knocks on the tree 
he rouses an army. Out of the little holes in the stem the 
members of the bodyguard stream in thousands, angrily 
excited. And this is the reception the leaf-cutters get. 
There is sometimes an Imbauba-tree without a bodyguard, 
but it is soon stripped by the leaf-cutters. Moreover, 
when Schimper found near Rio de Janeiro a kind of Cecro- 
pia without the pre-formed doorways (botanically inter- 
pretable), and without the palatable nutritive material 
and therefore without a bodyguard, and yet not defoliated, 
he discovered that this was an exception proving the rule, 
for a covering of slippery wax on the stem of this species 
made it difficult for the leaf-cutters to climb up. 


Criticism of Myrmecophily 


All this sounds very plausible, and it is almost against 
the grain to turn to modern criticism, such as may be 
found in Professor Neger’s masterly Biologie der Pflanzen, 
to which we are much indebted. But it is urged, for 
instance, that the bodyguard is not nearly so necessary as 
has been asserted; that the acacias and Imbaubas are very 
prolific; that many ants that render no benefit are fond of 
the dark, dry cavities of plants that need no protection; 


ANTS AND PLANTS 89 


that the bodyguard cannot be always credited with either 
success or courage; that the ants inside the hollow stem of 
the Cecropia do harm by attracting the attention of 
destructive woodpeckers; that the food afforded by even a 
large _ Imbauba is not nearly enough to sustain the body- 
guard. And this does not exhaust the criticism. 

Yet account must be taken of the simple fact that the 
natives of Java have been in the habit for a long time of 
utilising a large red ant to defeat the incursions of a beetle 
that destroys the precious fruit of the mango-tree. They 
arrange bridges of rope, or the like, from tree to tree, 
so that the ants, which are inveterate enemies of the 
beetles, may move about freely. If this works well, as it 
seems to do, why should we be ultra-sceptical in regard to 
the protective value of the bodyguard ants? What seems 
to be unsatisfactory in the theory of myrmecophily is the 
exaggeration of the adaptations by which the plants are 
supposed to have answered back to their partners, and 
an inadequate appreciation of the alertness with which 
ants are always on the outlook for some new niche of 
opportunity. 

That the ants have wrought out transmissible modi- 
fications on the plants which they frequent is exceedingly 
improbable; that the ants have turned the inborn 
peculiarities of certain plants to their own advantage, yet 
without serious damage to their hosts, is exceedingly 
probable. The story of myrmecodia is instructive. 
These are great swellings, sometimes two feet across, on 
the tubers of some plants related to coffee. They are 
riddled with passages and tenanted by crowds of ants; 
and they were interpreted by Beccari as direct responses 
on the part of the host-plants to the industry of the 
tenants. But Treub soon proved that the galleries are 
present, even when the ants are absent; and it is now gen- 
erally admitted that the primary significance of the 
myrmecodia is as absorbing-organs for the plant. 


90 SCIENCE, OLD AND NEW 


The instances we have given of inter-relations between 
plants and ants are only samples, but they must suffice. 
There are many ants that grow fungi and the leaf-cutters 
prepare a culture bed for fungoid growths, by chewing 
their collected leaves into a green paste; and there are 
ants that interfere in a high-handed way with the remark- 
able triple alliance established between (A) a beetle, (B) 
a kind of cochineal insect, and (C) the leaf-stalk of a 
leguminous tree! We have said enough to illustrate the 
general tendency in animate nature to link one living 
creature to another in a complex web of life. 


ol 


INSIDE AN ANTS’ NEST 


OI 





INSIDE AN ANTS’ NEST 


ONE of the uses of science is to make the opaque trans- 
lucent. If we really know the anatomy of an animal we 
can see through it. In the case of a snail within its shell, 
for instance, we can see the heart beating in its proper 
place; we can see the liver and kidney in their proper 
places, both very active; and so with the other organs. 
Similarly, the anatomist can see right through the human 
body, and the botanist can see what is going on in the 
living parts of the stem of a tree. The embryologist who 
knows his business can, without looking, see what is going 
on inside the egg-shell on each of the twenty-one days of 
the chick’s development. Our present desire for trans- 
lucency is none of these; it is to see inside an ants’ nest, 
as if its walls were made of glass. As in the case of 
“‘“observatory-hives’’ for bees, so, by means of ‘‘for- 
micaries’’ for ants, this close scrutiny has been made 
possible to ordinary people. For experts lke Professor 
Forel, who has been scrutinising ants all his life in wild 
nature as well as in the laboratory, what goes on behind 
the curtain is quite clear. Can we form some impression 
of the things that happen inside the ants’ nest, just as we 
might in regard to the processes that take place in a 
human factory? Let us, for a little, borrow Forel’s 
spectacles. 


93 


94 SCIENCE, OLD AND NEW 
Resting 


In the open we see ants extraordinarily busy; they seem 
indefatigable; their industry is an obsession. No creature 
could live long at their rate, and we know that in summer 
the worker hive-bees are very short-lived—little more than 
amonth. Among ants, however, there are resting periods 
within the nest. An individual worker comes in with a 
crop full of honey; the indoor attendants make it disgorge; 
and then it is packed off to bed. It is often very tired, 
unwilling to pull itself together even when a danger 
signal is “‘sounded,” but after a rest it returns to its 
labours. That is one thing to be seen inside the ants’ 
nest—rest. ‘The less we say of ‘“‘sleep”’ the better, for we 
do not know much about sleep among backboneless 
animals. What we are sure of is that the ants get tired, 
and that they sink into a sort of collapse from which they 


do not like to be roused. ‘‘Yet a little more slumber,” 
they seem to say, ‘‘yet a little more folding of the 
antenne.’’ When danger forces them to get on to 


their feet they move sluggishly, as if half awake, and 
they do not rescue the cocoons as normal ants always do. 


Silent Conversation 


Another thing that goes on inside the ant hill is silent 
conversation. There is a sort of deaf-and-dumb alphabet, 
the instruments of which are the feelers or antenne. 
These mobile and richly innervated structures, which are 
also the smelling organs, are used in passing the time of 
day. One ant strokes another’s antenna, and the other 
ant answers back. So it goes on alternately. We do not 
know what they talk about, but we think it must be about 
old times: ‘‘You remember that feast of honey.” 
Sometimes an ant will strike another hard with its jaws 
when it is breaking some rule or remaining careless in face 
of danger. But that isa different kind of talk. 


INSIDE AN ANTS’ NEST 95 
Care of the Young 


Much of the internal life of the nest is concerned with 
the young. The workers sometimes help the queen in her 
egg-laying, licking and massaging her. They carry away 
the laid eggs and deposit them in a suitable place, licking 
them repeatedly. Sometimes they are so fond of the eggs 
that they eat them; and when workers lay eggs, as they 
sometimes do, they have been known to eat them on the 
spot. The unnatural is apt to occur when the evolution 
of a large societary form perturbs the ordinary instincts of 
the individual, for we must face the fact that the success 
of the ant-community depends on a semi-repression of the 
workers. We do not think that Socialists would refer so 
often to the success of ants if they knew a little more about 
the seamy side. 

When the larve are hatched out of the eggs they have 
to be fed, and the workers disgorge honey or chewed food 
into their mouths. The larve have to be licked all over 
very often, and they have to be carried from one part of 
the nest to another, according to the temperature. When 
the larvee become pupz they need no more food, but the 
cocoons have to be transported from place to place, and 
they have to be brushed. Finally, the workers may have 
to cut the wall of the cocoon to let the young ant out, and 
they may help to set the youngster on its feet. When 
there is real danger to the ant hill some of the workers rush 
into the interior, and the news passes from antenna to 
antenna. Then there is the familiar hurry-scurry—not a 
sauve qui peut, but “‘save the children,” for each worker 
seizes a cocoon and does its utmost to remove it to a place 
of safety. Here the altruistic instinct reaches a high level. 


Toilet 


A good deal of time is given to personal toilet. There 
is an energetic use of comb and brush, of tongue and 


96 SCIENCE, OLD AND NEW 


mandibles, for ants are scrupulously cleanly. Forel tells 
us that even the most agile worker cannot wash its own 
head, and this necessitates a very interesting mutual 
toilet, which seems to be greatly appreciated. This is not 
to be confused with the way in which a hungry ant caresses 
a well-fed ant with its feelers, and induces it to disgorge 
something of its abundance. 


The Stores and Chores 


Another domestic industry is looking after the stores. 
The nutritive material has to be collected, but it may also 
have to be treated so that it does not sprout or rot; it has 
to be stowed away where moulds do not corrupt; it may 
have to be dried in the sun and re-stored. Sometimes it 
is made into biscuits, but that is another story. In 
unfriendly regions, like deserts, the storing industry is of 
great importance, and in the Messor ants of the Sahara 
there are deep and spacious underground galleries in which 
food is accumulated for the dry season. How quaint in 
this connection is a caste of worker honey-ants of the 
Garden of the Gods in Texas, where the crop is exaggerated 
to form a honey-pot. Half a hundred capitalistic honey- 
pots hang from the roof of the nest, and an ordinary 
worker keeps them in good humour. When compelled, 
an animated honey-pot disgorges its stores to two or three 
workers. That this strange adaptation is the result of a 
sort of enforced over-nutrition of large-sized workers is 
indicated by Professor W. M. Wheeler’s experiments, 
for he has been able to produce the animated honey-pots 
by persistent over-feeding of young workers of the large- 
sized variety. Here we might also refer to those ants that 
keep cows in the form of green-flies or aphids, which they 
care for just as if they were domesticated animals. They 
milk them for the sake of the sweet juice which they readily 
exude. Then there is the story of the leaf-cutting ants. 


INSIDE AN ANTS’ NEST 97 


Other Activities in the Nest 


Another internal activity has to do with the guests and 
pets—the tiny aromatic beetles in particular, which are 
to the ants like Pekinese dogs toman. They are use- 
less luxuries, looked after because they are pleasant. 

On rare occasions there is a great to-do when a flitting 
has been decided on. Preparations have to be made for a 
huge mobilisation of Liliputians, for there may be 100,000 
individuals in the nest of a Meadow Ant. In many cases, 
it must be understood, the ant community is one huge 
family; in other cases, as with the enormous ant hills of 
pine leaves in the Scottish Highlands, there are several 
large families in one community. 

What goes on inside an ants’ nest? There is resting, 
there is silent conversation, there is nursing in the wide 
sense, there is vicarious parental care, there is elaborate 
personal toilet, there is the care of stores, there is the 
petting of guests, and there are preparations for flitting. 
But these do not complete the list of internal activities. 
Thus, there is sometimes an exhibition of frolicsome gym- 
nastics, when the inmates of the nest seem to let them- 
selves go, indulging in extraordinary exercises which are 
either games or something horribly Freudian. The 
evidence is in favour of regarding them as spates of 
playfulness! 














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SLAVERY AMONG ANTS 


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SLAVERY AMONG ANTS 


THE ways of a community of ants often appear like 
anticipations, sometimes like caricatures, of social be- 
haviour among men. One thinks of the division of 
labour, the esprit de corps, the mutual aid, the obsession 
of the community’s claims, the capitalisation of energy, 
the occasional domestication of other insects, and the 
occasional cultivation of plants. There is also the keeping 
of pets and the Liliputian warfare. Strangest of all, 
perhaps, is the fact that some ants keep slaves, as Pierre 
Huber discovered in 1810. To this naturalist, indeed, the 
fact of slave-keeping seemed so upsetting that he made a 
plea for calling the slaves ‘‘auxiliaries.’’ It is interesting 
to inquire whether the word ‘‘slavery’’ which Huber 
rejected is justifiable or not, and the inquiry is made 
easier by the recent appearance of the fourth volume of 
Auguste Forel’s fine book, Le Monde Sociale des Fourmts 
(1923). What are the facts of the case in regard to the 
strange custom to which the term slavery is applied? 


Raids of Red Ants 


One of the most plastic of ants, apparently showing 
intelligent profiting by experience as well as inborn 
instinctive dexterity, is the common Red Ant, which 
extends from Britain to Japan. Forel calls it Raptiformica 
sanguinea, but the first two syllables of this long name are 

rol 


102 SCIENCE, OLD AND NEW 


often omitted. In the middle of summer a large band of 
Reds leave their nest and search for a community of 
Serviformica glebaria or some other ant known from 
experience to be suitable. The expedition sets out in the 
morning, and may last into the afternoon. It is carefully 
organised without any fuss or flurry. When a suitable 
nest is found, the column of Reds spreads out into a cres- 
cent, or even into a circle, and the assault begins. The 
workers of the attacked colony rush out, each with a pupa 
or cocoon in its jaws in the usual altruistic fashion of ants. 
But the cocoons are snatched away, and there is soon a 
line of Reds carrying the captives back to the Red nest. 
The assault becomes keener, for the besiegers post guards 
at the gateways and prevent escape. They penetrate 
into the interior and steal pupze from their very cradles. 
According to Forel, the aggressors rarely do any violence 
unless the attacked begin to bite, and the degree of 
recalcitrance differs from species to species. In some cases 
there is a vigorous sortie and a determined attempt to 
break through the ring. But the Reds are too numerous 
and too clever, and the capture of cocoons—it is, after all, 
a sort of “‘baby-snatching’’—goes on until the Reds feel 
that they have enough. It will be understood that in this 
case, and in many others, in the New World as well as in 
the Old, there is no attempt to capture adults. Thus the 
slaves-to-be have no knowledge of any conditions except 
those into which they are hatched. We cannot but won- 
der whether they have any dim memories of having been 
larvee somewhere else—that is to say in the parental nest. 
Forel reports an interesting case where the Reds captured 
some Meadow Ant pupz and hatched them out into slav- 
ery in the usual fashion. But one day when the slaves 
were bustling about, working for their masters (or mis- 
tresses rather) they happened to meet their old mother. 
Whereupon they carried her to the Red nest, which hap- 
pened to be at that time queenless. This looks at first 


SLAVERY AMONG ANTS 103 


sight almost providential, but the inevitable outcome 
was that the Red Ant nest became a Meadow Ant nest. 
For the Meadow queen could not, of course, produce any- 
thing but Meadow offspring! 


Amazon Ants 


Slave-keeping is much marked among the Amazon 
ants, of which the European Polyergus is a good repre- 
sentative. For these Amazons are entirely dependent 
on their slaves; they cannot feed themselves and they 
cannot feed one another. Even in the presence of honey 
and other palatable food, they will perish of hunger, for 
the feeding instinct isin abeyance. They have to be fed. 
But put a single worker-slave in the midst of the Amazons 
and she immediately supplies food in response to their 
solicitations. Not only is active feeding in desuetude, but 
the Amazons are unable to attend to the brood, and they 
have lost the art of building. But we must not think of 
them as degenerates, for they are fearless fighters, and will 
allow themselves to be killed rather than retreat. With 
their large sickle-shaped jaws they grip the head or body 
of their adversary, and they are able to give a good account 
of themselves. 

Forel has given us circumstantial details in regard to 
the raids of the Amazon ants, and there is no more re- 
markable chapter in the whole book of natural history. 
The raids occur in the summer months, from the end of 
June to the beginning of September; they usually start in 
the afternoon, when the temperature is comfortable, 
and last for three or four hours. There may be 375 to 
1400 Amazons in an army—all of them ‘‘workers,”’ if it is 
permissible to apply this term to such non-industrial 
militant creatures. The rate of the marching column, 
which sometimes has a length of two or three yards, may 
amount to about four yards in a minute, but it is much 


104 SCIENCE, OLD AND NEW 


reduced when the captured pupz are being carried home. 
There is no field-marshal leading the army; on the con- 
trary, the Amazons in the vanguard periodically pass back 
to the rear. This seems to involve the raiders in consider- 
able indecision, and even when they utilise scouts who 
have discovered an underground slave-nest, the army 
sometimes loses its way. They call a halt with soundless 
signals and make a few tentative sallies, but if they are 
unsuccessful they become tired and discouraged, and 
turn homewards again. It is important that they should 
reach shelter before they are overtaken by the cold of 
evening. 


Two Striking Details 


Many of the details of the slavery among the Amazons 
are passing strange, but we must be content with mention- 
ing two. The Amazon worker gets astride of the stolen 
cocoon and carries it between its front legs, for it can move 
most expeditiously in this fashion. But it cannot mount 
on the larger cocoons, which hatch into queens and males. 
From the fact, then, that the slaves are all workers, 
normally non-reproductive, it follows that the Amazon 
community cannot be overpopulated by slaves. It also 
follows that as the hard-worked slaves die off they must 
be replaced by fresh captures. 

When food is scarce and the weather very hot the slaves 
sometimes mutiny. It gets on their nerves to be continu- 
ally importuned for food by their militant mistresses. So 
a number of them combine to drag an Amazon to some 
distance from the nest. But the Amazon is so well 
armoured that it is difficult for a slave to do much harm, 
and the Amazon may be back at the nest before the 
revolutionary slaves have returned. If a slave should 
become too refractory and troublesome, the Amazon 
puts her big jaws round its head—and all is over! But 


SLAVERY AMONG ANTS 105 


one is not sorry to learn that these revolts of the slaves 
do occur, and that there is at least one American species 
in which the slaves are sometimes successful in asserting 
their independence. 


Evolution of Slavery 


An interesting point in connection with slavery among 
ants is that there are various grades, forming an evolu- 
tionary series. Among the Reds, with which we began, 
it is not necessary to have slaves, though it is advantage- 
ous. Among the Amazon ants the utilisation of slaves is 
obligatory, for without them the Amazons would die. 
But between these two grades there are intermediate 
stages, such as are represented by the European and 
North American species of the genus Harpagoxenus. 
If there is anyone who still feels unable to adopt the 
evolutionary way of looking at things, he should give 
some study to the species of ant within the genus Strongy- 
lognathus. For the different species show many grada- 
tions. Thus the species S. testaceus has become practically 
a parasite, yet shows what Forel calls racial rem- 
iniscences of having had slave-owning ancestry! An- 
other species makes slave-making raids by day and yet 
another species by night. In S. alpinus there is a droll 
climax, with which we may fitly conclude our story. The 
slaves are included in the raiding expeditions, and are 
used to make more slaves of their own kith and kin; if 
there is fighting to do, it is left to the slaves; the slave- 
owners’ role is one of intimidation, though they sometimes 
condescend to carry their captives home. 


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XIV 


BEETLES AND BUGS IN PARTNERSHIP 


107 





BEETLES AND BUGS IN PARTNERSHIP 


ONE of the most interesting of recent natural history 
stories is Professor W. M. Wheeler’s account of the social 
beetles that live in the swollen leaf-stalks of a peculiar 
leguminous tree (Tachigalia), indigenous to the Guianas. 
The plant occurs as a young shade form, a few feet high 
and with few leaves, and as a sun form, which is a real 
tree, with a crown of foliage at the summit of a very - 
slender trunk, 40 to 60 feet in height. The hollow leaf- 
stalks are likewise tenanted by ants, and both the beetles 
and the ants cultivate coccid insects. As we shall see, 
there are other wheels within wheels. 


A Triple Alliance 


The keystone of the animate arch is the leaf-stalk or 
petiole of the Tachigalia. It is swollen in spindle form 
and is at first filled with juicy pith. This soon dries up 
and turns into loose fluffy amber-coloured tissue, which 
contains some very nutritive substance. Into this at- 
tractive shelter a queen-ant (one of four species) gnaws 
her way and closes the door behind her. She lays eggs 
and rears a brood of workers in the amber-coloured fluff. 
These workers open the door and go out and in. Soon, 
however, there are other inmates, which come in or are 
brought into the swollen petiole. These are coccid in- 
sects or mealy bugs, of a particular species, of course, 


109 


110 SCIENCE, OLD AND NEW 


which attach themselves to the nutritive tissue and find 
an abundant supply of sap. So abundant, indeed, that 
the mealy bugs overflow and afford the ants a welcome 
supply of food. From one shelter another may be colon- 
ised, and the broods of several queens probably agree to 
live in harmony on the tree. If you knock at the door the 
workers rush out in angry crowds. An interesting point 
is that on any one tree there is only one kind of ant 
tenanting the swollen petioles. There are indeed leaf- 
cutter ants exploring, there are thief ants sneaking into 
the shelters, and there are non-aggressive ants who enter 
every hole and corner, but each tree has only one kind 
of ant-guest cultivating mealy bugs in the swollen petioles. 
So far then we have to do with a three-cornered inter- 
relation—the ‘‘myrmecophilous” Tachigalia tree, the 
special ant-tenants, and the mealy bugs that are middle- 
men between the two others. 

It is time to turn to the beetle which Professor Wheeler 
found in the same inter-relation as the ant, 7.e., living 
inside the swollen leaf-stalk and utilising mealy bugs. 
It is a small narrow Silvanid beetle, dark chestnut brown, 
not very unlike some kinds of ants. Except when hungry 
or disturbed it is rather sluggish, and the observer never 
saw it fly. A pair of beetles resolve to set up house in a 
swollen petiole, either in an intact one or in a deserted 
one. In either case they make an entrance for themselves. 
If they have chosen a previously occupied house there is a 
good deal of cleaning necessary, but this is done somewhat 
perfunctorily by packing the refuse into the narrow ends 
of the spindle-shaped cavity. After things are tidy the 
female lays a few eggs which develop rapidly. Then 
enter the mealy bugs, which attach themselves to the 
amber-coloured tissue and are utilised by the beetles just 
as by the ants. But the beetles are able to feed on the 
vegetable tissue directly as well as indirectly. As the 
space is limited and as everything depends on the con- 


BEETLES AND BUGS IN PARTNERSHIP iit 


tinued proliferation of the nutritive tissue, the inside of 
the petiole is kept in good order. The “‘frass”’ or undi- 
gested stuff, passed from the food-canal of the beetles and 
coccids, is disposed of in orderly ridges, and a little is 
used to build a circular tower round the opening. Here 
one of the beetles sometimes mounts guard, occasionally 
projecting his feelers and waving them about—a quaint 
sight on the surface of a plant! The inmates of the petiole 
may now consist of the parent-beetles, a dozen or so 
youngsters of various ages, and about as many mealy 
bugs. In some of the milk-eating tribes of Central Africa 
every child has its special cow, so there is usually a mealy 
bug for each young beetle. Soon, however, there is a 
second generation of beetles and the mealy bugs also 
multiply. There are deaths, of course, and consequent 
additions to the kitchen-middens in the narrow ends of 
the spindle, but the house becomes overcrowded. Then 
the beetles begin to flit, singly or in pairs, and new house- 
holds are started in other leaves of the tree. It should 
be noted that while the larval and adult beetles are able 
to eat the amber-coloured tissue, they always solicit and 
utilise the sugary overflow of the coccids. 

Only the female mealy bug of the Tachigalia has been 
seen—a squat pinkish creature, three millimetres in length, 
covered dorsally with white mealy wax. There are two 
pairs of minute dorsal ostioles which possibly secrete some 
attractive or repulsive substance. In some related forms 
droplets have been detected, but not in this species. The 
honeydew which the ants and beetles are so fond of is 
passed out from the end of the food-canal. If the mealy 
bugs are the cows of the beetles, in the sense in which 
Linneus called aphids vacce formicarum, then the 
honeydew corresponds to cow-dung. When a hungry 
and thirsty beetle comes across a bug, it immediately 
proceeds to massage it with its club-shaped antenne. 
It beats vigorously, using the feelers alternately, re- 


112 SCIENCE, OLD AND NEW 


minding the observer of an energetic piano-player, or, 
perhaps, of an exponent of musical slates with a gloved 
drumstick in each hand. Whenever a clear drop is 
emitted it is greedily swallowed. Then follows more 
percussionary massage. It is hard work, for the beetle 
has sometimes to beat for half-an-hour before it gets 
drops enough. Moreover the beetle sometimes tackles 
a dry coccid and may beat for an hour without getting 
a drink. An ant would never persist so long, but the 
beetle has not the brains of an ant. Many beetles and 
their larvee too may crowd around one bug and drum on it 
together. But only one at a time can imbibe the clear 
droplet. It is no case of ilka beetle having its ain drap 
o’ dew. So there is hustling and butting among the beetles. 
This strikes a note that is not instinctive. 


Mutual Benefits 


Where, it may be asked, do the mealy bugs’ interests 
come in? Part of the answer is that they cannot get inside 
the petiole unless ants or beetles make a door. It is 
possible, moreover, that the massaging is good for their 
health. An interesting detail is that when leaves are 
cut off and become dry, the coccids drop from the grooves 
of nutritive tissue in which they were attached; their bodies 
become attenuated and somewhat shrivelled; the larval 
beetles suffer in the same way; the adults share in the 
general discomfort and restlessness. Then the beetles, 
both young and old, turn on one another and canni- 
balism runs riot for a brief space. But this does not occur 
in a state of Nature. 


Wheels Within Wheels 


Professor Wheeler soon discovered that the life of the 
beetles was not an easy one. ‘They occur only in the 


BEETLES AND BUGS IN PARTNERSHIP 113 


younger shade forms of the Tachigalia, for they cannot 
stand against the ants that colonise the larger tree-like 
forms of the plant. But before these arrive on the scene 
there are other enemies which invade the shelters. The 
worst of these is a little thief-ant Solenopsis that works 
at night and burgles the beetles’ homes. It gets in at the 
unguarded door or bluffs the porter, and it devours the 
beetles both young and old. What it does to the mealy 
bugs is uncertain. They are compared by Dr. Wheeler 
to the cattle in a disturbed country; in most cases they 
change masters; occasionally they are devoured. But 
apart from the dangers incidental to the struggles between 
beetles and ants, the mealy bugs have enemies of their 
own—the predaceous larve of a small Coccinellid beetle, 
the maggots of a midge which enclose the bugs in a white 
web and devour them at leisure, and a Hymenopterous 
parasite which develops inside the bug. Truly wheels 
within wheels! 

On a few occasions in his studies at Kartabo in Guiana, 
Professor Wheeler found the petioles of Tachigalia 
tenanted not by the beetle (Coccidotrophus socialis) 
whose ways have been described, but by another of dif- 
ferent structure and similar habits. It seemed like a poor 
copy of the first—‘‘a feeble, anzemic and harried species 
on the verge of extinction.”” The probability is that both 
kinds of beetles were at first vegetarian, that they found 
open petioles which ants had left, that they learned the 
palatability of the amber-coloured tissue, that they 
discovered from the ants the trick of utilising mealy 
bugs. But there is many a ‘“‘perhaps”’ in the story. 
There are some other beetles that live in companies, but 
outside of the order of ants there are only two or three 
instances of insects utilising bugs as cows. The major 
problem is to picture the origin of that remarkable 
habit among beetles. The larval beetles are more alert, 
restless, and inquisitive than the adults; they massage 


114 SCIENCE, OLD AND NEW 


with great vigour; they have mouth-parts well suited 
for spooning up the sugary drops. Perhaps the habit 
began with them and they taught their parents. Perhaps, 
on the other hand, the adult beetles picked up the idea 
from the ants, and it should be noted that when a beetle 
enters an open petiole which the ants have deserted, it 
often finds willing coccids already there. Professor 
Wheeler hints at another hypothesis, but rejects it as 
rather far-fetched, that the habit may have arisen as a 
modification of a sexual activity, for the stroking of the 
female beetle by the male during the courtship is pre- 
cisely like the stroking of the coccids. In any case we 
have to congratulate Professor Wheeler on his discovery 
of the facts concerning a singular pattern in the web of life. 
Perhaps there are fifty different threads meeting in the 
Tachigalia tree. 


XV 


INSECT MUSICIANS 


115 














Bie ia rie Age ’ a ‘4 ey 
= iS ha 
ee a tok pope iy ya “haa 
atk a Bitsy aaa 


ae 


INSECT MUSICIANS 


In the course of evolution the voice has justified itself 
in many different ways, but its primary use was to ex- 
press and invite love. The first words in the world were: 
‘Arise, my love, my fair one, arise and come away”’; 
and in simple-minded animals like frogs the only use of 
language is still the first one—to serve as a sex-call. 

But there may be wordless voices. Just as an ant 
brings tidings to her neighbour by tapping its body with 
her antenne, a sort of Morse Code, so there are many 
insects that express their love by means of instrumental 
music. Very energetically the males fiddle with one hard 
part of the body against another, say a leg against a wing, 
thus producing a chirping or trilling, technically called 
stridulation. This is very common in the cricket- 
locust-grasshopper-katydid order (Orthoptera), and it 
occurs in diverse ways. 


A Variety of Instruments 


In the burrowing mole-cricket, a ‘‘bow’’ on the under- 
side of one fore-wing is rapidly rubbed against a “‘string”’ 
on the underside of the other fore-wing; and after a while 
the two wings reverse their mutual relations. In crickets 
the apparatus is more complicated but it is still confined 
to the fore-wings. The note is sometimes so shrill and 
penetrating that it can be heard a mile off. In locusts 

117 


118 SCIENCE, OLD AND NEW 


and true grasshoppers there is a row of minute beads or 
pegs on the hind leg, and this row is scraped against 
a sharp ridge on the outer surface of the front wing. This 
sets the wing into very rapid vibration and a sound re- 
sults. In the “ green grasshoppers’”’ and katydids the musi- 
cal instrument consists of a file at the base of the left 
fore-wing and a ridge at the base of the right fore-wing. 
These work against one another, and the sound seems 
to be mainly due to the rapid vibration of the right fore- 
wing. The katydid musician has much pertinacity but 
a short repertory; over and over again, with occasional 
slight variations, he says: ‘‘Katy-did; O-she-did; Katy- 
did-she-did.”” It is interesting, however, that the diurnal 
music is a little different from the nocturnal, and a passing 
cloud may change the former into the latter. It has been 
shown with great precision that the number of calls per 
minute varies with the temperature. Indeed one can 
use the number of calls as a thermometer! 


What the Music Means 


We know precise details in regard to the various 
musical instruments used by insects, and the general 
meaning of the performance is clear. It is an expression 
and an evocation of sex-excitement. The male grass- 
hopper fiddles away hour after hour; he does this with 
great zest; it means for him that he wants a wife. It is 
also certain that the females draw to the musicians; in 
some cases they answer softly back. For although strid- 
ulating instruments are usually confined to the males, they 
are present though not so well developed in a few females; 
and these have been known to use them. The main 
difficulty in interpreting the serenading is that we know 
very little in regard to the sense of hearing in insects. 
Their sensitiveness to vibrations is often exquisite but 
only in a few cases has their responsiveness to sound 


LNSEGCE MUSICIANS 119 


waves been satisfactorily proved. Some ants that have 
musical instruments are nevertheless strangely deaf, 
and Forel has not been able to satisfy himself that they 
hear in our meaning of the word. In some cases, earlike 
organs are present, though the insects produce no sound. 
In one of the green grasshoppers there is no sound-produc- 
ing instrument, but the creature turns upside down and 
drums on the ground with his tail. This suggests vibra- 
tions as much as sound waves. 

It is probable, however, that in most cases the females 
hear the excited serenaders, for they certainly come. 
The instrumental music must be effective, for the instru- 
ments are very elaborate and their evolution must have 
taken a long time. The amount of energy devoted to the 
performance is extraordinary. Very interesting is the 
way in which groups of male ‘‘green grasshoppers”’ or 
Locustids shift their ground like itinerant musicians. 
They draw blank and they try another place, just as male 
corncrakes try field after field with their ‘‘creeking”’ call. 
It may be noted that a male mosquito answers back, by 
vibrations of his antennary hairs, to a tuning fork pro- 
ducing a note corresponding to the female’s hum. 


Cicadas and Other Instrumentalists 


In Cicadas, which the ungallant Greeks called happy 
‘‘in having voiceless wives,’’ the musical instrument is 
on lines quite different from that of the fiddlers. A vi- 
brating membrane on the under surface of the body is 
set in motion and kept in motion by the contractions of 
a special muscle, as a drum-head by strokes of the drum- 
sticks. There is also a large resonating cavity which 
greatly increases the carrying power of the sound. Hun- 
dreds of male Cicadas combine in an orchestra, and the 
noise they make requires to be heard. Gradually the 
females draw near. 


120 SCIENCE, OLD AND NEW 


Among butterflies and moths there are occasional 
instances of the production of sounds by rubbing one 
wing against another, or by working on a wing with a 
leg, or by some other method. There is an Alpine Moth 
which produces when flying a very distinctive note, due 
to the vibrations of the margins of the anterior breathing 
apertures, and intensified by a resonator. When the 
female hidden among the grass hears the call of the low 
flying male, she trembles all over and flutters her wings, 
thus attracting his attention. Among beetles there is a 
widespread occurrence of stridulation, usually by working 
a rasp against a scraper, and it is interesting to find that 
when the instrument is present it is usually in both sexes, 
sometimes even in the grub. In one case at least the ap- 
paratus is confined to the female. We cannot profess to 
understand the meaning of sound-production in beetles; 
but in the case of the death-watch, where the male knocks | 
his head against the wood, the tapping is surely a love- 
signal. 

The sounds produced by rapidly flying insects like bees 
vary considerably from time to time, and may be used 
to express changing emotions. The sounds are in part 
due to the movements of the wings which beat with 
sufficient rapidity and regularity to produce a definite 
note. A fly may make three hundred strokes in a second! 
But apart from the wing-tone there is often a buzz or 
hum, due to the rapid vibration of a membrane or pro- 
jection behind the breathing openings. But we have 
said enough to illustrate the variety of instrumental music 
among insects, and to make it plain that its usual meaning 
is to express and evoke what we may call, in inverted 
commas at least, ‘‘Love.”’ 


XVI 


GARDENER INSECTS 


{21 





GARDENER INSECTS 


THE lover of insects, who is born not made, watches by 
an inexhaustible well of surprises. There is always 
something new in entomology. Thus Mr. William Beebe, 
the fortunate travelling naturalist of the Zoological 
Society of New York, a man with an infinite capacity 
for taking pains, but likewise with a knack for discerning 
the significant, has told us in his charming story of 
The Edge of the Jungle, how he broke into the under- 
ground city of the leaf-cutting ants, and saw hordes 
of workers chewing and chewing at the leaves which 
their fellows had brought in. But they were not eating 
them, as some naturalists had supposed; they were mak- 
ing them into a green paste on which is grown a fungus 
or mould. This fungus seems not to be known outside 
of the underground city of the leaf-cutter ants; they 
have the monopoly. It forms, apparently, the exclusive 
food during the subterranean life of the ants, but they 
probably ‘“‘pick a bit”’ out of doors. 


Mushroom-Growers 


In his Naturalist in Nicaragua (1874) Thomas Belt 
got near the truth in regard to certain leaf-cutter ants. 
“I believe,” he wrote, “‘that they are, in reality, mush- 
room growers and eaters.’’ He pictured the leaf-cutting 
industry, the throngs of ants coming on their forest- 


123 


124 SCIENCE, OLD AND NEW 


paths which reminded him of the streets of London, and 
the disappearance of the leaves into the recesses of 
earthen ant hills. But it was reserved for Modller to see 
the workers within the nest chewing and teasing the 
leaves into a tough paste, which is stored in large chambers 
and used as a bed for a fungus. The ants do not allow 
fructifications to grow, and they cut off the free threads 
of the fungus which tend to spread along the walls of the 
passages. The result of their labours is an abundant 
somewhat cauliflower-like growth on the beds of chewed 
leaf. Useless fungi are weeded out, but it is probable 
that the chewing affects the paste in some subtle way, 
so that it 1s suitable for the nutritive fungus but unsuitable 
for intruders. As the leaf-soil becomes exhausted it is 
removed in little balls, and fresh material is provided. 
Without the fungus the ants will starve, and without the 
gardener ants the fungus will run riot for a little and then 
die off. As we have said, it is not known outside the 
ants’ nest. When a queen flies off to start a new com- 
munity she takes a pill of the fungus with her in a pouch 
beneath her mouth. But in the new home there is no 
store of leaf-paste, for the queen has as yet no daughters 
to collect for her. What happens is remarkable. The 
queen plants out the fungus in the nest, and manures it 
with fluid from the food-canal. By-and-by her worker- 
daughters do the same, and it may be that the fluid, 
besides keeping the fungus growing, acts as a ‘‘selective 
steriliser.”” Soon, however, there is an importation of 
cut leaves, and a true garden is established. From 
an evolutionist point of view it is important to notice 
that there are other ants that grow fungi, and that the 
arrangements form a graduated series leading up to the 
climax we have described. Thus some use a variety of 
vegetable materials as a basis for the fungoid growth; 
they are not so specialised as those studied by Belt, 
Moller, and Beebe. 


GARDENER INSECTS 125 


In some cases, such as the common Black Ant of 
Europe, that makes its home in hollow trees, there is 
often a particular kind of fungus growing on the walls of 
the passages of the nest. Its name is significant—Septos- 
porium myrmecophilum, but, so far as we are aware (a 
necessary saving clause, since knowledge of these matters 
grows so quickly), the ants do not cultivate it, though 
they are said to relish the dew-like drops that appear on 
the ends of the fungoid threads. Such a case seems to us 
almost as interesting as the indubitable cultivation seen 
in the leaf-cutters. For it gives us a hint of the way in 
which the business might begin. Surely we should ex- 
pect animals, especially on the instinctive line of life, to 
utilise rather than to invent. If a fungus naturally grew 
on the walls of the passages of the nest, the ants would 
tend—finicking creatures as they are—to eliminate it 
when disadvantageous; but they would naturally let it 
flourish when there was something in it that profited. 


Termites as Gardeners 


Everyone knows that termites, or ‘‘white ants,” are 
architects of distinction, for they build great strongholds 
of salivated earth sometimes ten feet high, sometimes 
stable enough to bear a man’s weight. Yet inside these 
ant hills there are nurseries and assembly rooms, royal 
chambers and store houses, passages and secret staircases, 
attics, too, and cellars. The fact is the termites are 
architects who care as much for interiors as for exteriors. 
But they are gardeners as well as architects; they are, to 
use Belt’s phrase, ‘‘mushroom-growers.”’ This is particu- 
larly interesting, because the custom of cultivating fungi 
must have arisen independently among the termites. 
For although we call the termites ‘‘white ants,” they are 
not even nearly related to ants, and few of them could 
be called white. Some of them are so far from being white 


126 SCIENCE, OLD AND NEW 


that they are black! The fungus-gardens of the termites 
are seen at their best in Ceylon, and the characteristic 
feature is the construction of a maze of chewed wood with 
labyrinthine passages, on the walls of which the fungi 
grow. The labyrinth may be the size of a hazel-nut or 
the size of a man’s head, but the idea is always the same 
—a multitude of passages, on the walls of which the fungus 
produces minute white spheres of very palatable quality. 
According to fungologists, these spheres should produce 
spores, but that does not usually come off in the termites’ 
garden. But the termites have no doubt as to their nature, 
for that, from the termite’s point of view, is not simply 
food, but dessert. Most termites are wood-eaters, and it 
must be a great relief to get a meal of juicy mould. Pro- 
fessor Henry Drummond—of evergreen memory—said 
that there were places in tropical Africa where it was 
dangerous for a man with a wooden leg to go to sleep, 
because the termites would reduce his dependable arti- 
ficial limb to sawdust by the morning. A good story, no 
doubt, yet awfully true; for termites retard the spread 
of civilisation very seriously by their destruction of every- 
thing wooden. 

From our present point of view the important fact is 
that termites, which are miles away from true ants, are 
also given to utilising fungoid growths in their houses, 
though they do not weed them so carefully as do the leaf- 
cutters. When we note that at least one kind of termite 
carries home segments of leaves, we again raise the prob- 
lem—surely worth pondering over—of Nature repeating 
herself! 


Ambrosia Beetles 
Many beetles eat wood, but wood is poor feeding even 


when there is sap in it, for the sap that goes up the young 
wood consists of little more than water and salts. But 


GARDENER INSECTS 127 


some beetles that bore in fresh wood have discovered how 
to grow a mould that yields what is called ‘‘ambrosia.”’ 
The fungus lives on the wood and its sap, and it spreads on 
the walls of tunnels which the beetles make. The fungus 
collects and concentrates the food for the beetles and their 
grubs. In some cases the beetles do not eat the wood 
through which they bore; their food-canal contains only 
the ‘‘ambrosia’”’ cells of the fungus. It is interesting to 
notice that the burrows of the ambrosia beetles are 
practically confined to the sap-wood, for the fungus 
would not grow in the heart wood where the cells are 
almost empty. And another very interesting point is 
that the cultivated fungus does not seem to form spores 
or other elements specialised for propagation. It must 
be disseminated by the gardener-beetles themselves, and 
the probability is that they infect a new tree with surplus 
vegetative ambrosia-cells which have passed out undi- 
gested from their food-canal. Yet it seems to be curiously 
difficult for the botanist to grow a successful culture of 
ambrosia! 


Ambrosia Midges 


A remarkable linkage of lives has also been demon- 
strated in the case of certain gall-flies which attack the 
flowers of mulleins, scrophularias, and capers. Here there 
are wheels within wheels. First there is the gall, an answer- 
back which the plant makes to the irritation which follows 
when the gall-midge lays an egg in the soft tissue. In most 
cases the stimulus seems to be the secretion that oozes 
from the mouth of the larva that hatches out of the egg 
of the gall-insect. In the second place, within the cavity 
of the gall there is a fungoid growth, first pure white and 
then grey or black, and the ambrosia-cells of the fungus 
are rich in starchy material. 

The larve of the midge can obtain food from the wall of 


128 SCIENCE, OLD AND NEW 


the gall, but they usually thrive better when there is a 
vigorous growth of the fungus. None of these arrange- 
ments can be called perfect, however, for it sometimes 
happens that the gall allows of the growth of some weed 
of a fungus along with the ambrosial one—tares among the 
wheat, in fact. On the other hand, in his Biologie der 
Pflanzen, which includes a masterly discussion of all 
these linkages, Professor Neger insists that this symbiosis 
of gall-midge, flowering plant, and fungus is an old-estab- 
lished partnership, that works, on the whole, smoothly. 
Wherever the gall-midge spreads, its partner fungus goes 
with it—how exactly we do not know. For the midges 
are extremely delicate suctorial insects. It seems likely 
that the egg-laying organ of the female midge is infected 
with very minute spores of the fungus which sometimes 
appear on the surface of the plant. When the mother- 
midge lays an egg in the bud she unconsciously inserts 
a fungus spore as well. 

We have kept to one kind of gardening activity, the 
cultivation of fungi, but we are not forgetting the work 
of the agricultural ants of Texas and other interesting 
linkages between insects and plants. What we have 
said is enough, in the meantime, to illustrate the wide- 
spread tendency in Animate Nature to bind one creature 
to another in the Web of Life. 


XVII 


THE FLOWER AND THE BEE 


129 





THE FLOWER AND THE BEE 


ONE of the main trends of evolution has certainly been 
to link living creatures together, and one of the most im- 
portant linkages in history has been that between flowers 
and useful insect visitors, such as bees. Useful, because 
the bees, in getting pollen and nectar for their own pur- 
poses, bring about the cross-fertilisation of flowers. And 
this cross-fertilisation improves both the quantity and the 
quality of the seed. Throughout long ages the flowers and 
the bees, if we may keep to bees for a moment, have 
evolved together; and they are now fitted to one another 
as hand to glove. In many cases they are nowadays in- 
dispensable to one another, for many of the flowers are 
so specialised that they cannot be fertilised except by 
bees; while, on the other side, bees are so highly special- 
ised that they would all come to an end if there were no 
flowers that produced nectar. 


Linkages Determining Lines of Evolution 


This linkage, like many another, must in some measure 
determine the lines of further evolution; for the flower 
cannot safely change in a direction that would shut the 
door on its visitors; and the bees cannot safely change 
in a direction that would lessen their success with the 
flowers. The linkage is part of the well-woven web of life, 

re 


132 SCIENCE, OLD AND NEW 


and it tends, like social linkages of a profitable kind, to 
keep things from sliding back. One must be cautious, 
however, for it is possible that without insects to pollinate 
them flowers might fall back on virgin-birth (or partheno- 
genesis), and that seems to be occurring in such very suc- 
cessful flowers as dandelions. They still produce pollen, 
but it is not used. 


Bees Not Random Visitors 


Inside the seed-box of a flower there are possible seeds 
or ovules, each containing a single microscopic egg-cell. 
The possible seed will not become a real seed, that is to 
say, an embryo plant, unless this egg-cell is fertilised. 
Similarly, no one expects a chick to come out of the unfer- 
tilised egg of a hen, and the egg must remain unfertilised 
if there is no cock in the yard. The fertilisation of the 
microscopic egg-cell of the plant depends on the dusting 
of the tip or stigma of the pistil with appropriate pollen- 
grains produced by the stamens of another flower of the 
same kind. Cases of self-pollination, as in peas, oats, rice, 
are in a minority; in most cases the pollen is carried from 
another blossom by insects or by the wind. A suitable 
pollen-grain, caught on the moist surface of the stigma, 
sends out a long tube which grows down to the ovule, and 
a male element—little more than one of the nuclei—in the 
pollen-tube enters into intimate orderly union with the 
microscopic egg-cell. In the maidenhair tree and a few 
other primitive seed-plants the male element is a freely 
moving cell, as it is in mosses and ferns and in most 
animals. In all ordinary flowering plants the male element 
is a more or less passive cell borne to the egg-cell by the 
growth of the pollen-tube. But in all cases the essence of 
fertilisation is the same, the intimate union of male-cell 
and egg-cell; this is the beginning of a new individual. 

But this is only an introduction to what we wish to get 


THE FLOWER AND THE BEE 133 


at—namely, an answer to the difficulty which must rise 
in the inquiring mind: How is it that the bees do not mix 
up pollens hopelessly as they pass from flower to flower? 
If a humble-bee dusts the pistil of a red-clover with the 
pollen of an aconite, the flower will not be ‘‘much for- 
rarder.” The answer is threefold. Some insects are 
specialists; they know their flowers ‘‘like good botanists,”’ 
and they keep to them consistently. But, secondly, even 
when the insect is not a specialist it tends on a given 
journey or forenoon to keep to one kind of flower. What 
Aristotle observed, that bees do not fly at random from 
one kind of blossom to another, has been amply confirmed. 
The mouth-parts are suited for particular kinds of flowers; 
thus the hive-bee’s tongue is not long enough to reach 
the nectar of the ordinary corolla of the red clover, which 
is easily reached by the humble-bee. 

Moreover, of a summer morning, hive-bees pay con- 
siderable heed to the tidings brought in by the scouts, 
who inform them in some way or other, which flowers are 
most profitable at the time. It must be remembered that 
true bees deal very intimately with the pollen-grains; 
they moisten them with their mouths and put cakes of 
them in a depression or basket on one of the joints of 
the hind-legs, and the next joint is enlarged into a hairy 
brush. The pollen that is of use to the next flower is the 
loose dust entangled on various appropriate parts of the 
bee’s body, appropriate in the sense that they knock 
against the stigma and deposit the grains there. Finally, 
it appears that foreign pollen dusted on to the stigma 
usually dies; only the proper kind of pollen sends out a 
pollen-tube. Add these three points together—(1) the 
specialisms of insect visitors, (2) their consistency on a 
given journey, and (3) the specificity of the pollen, which 
only grows on its appropriate soil (the stigma of its kind), 
and you have the answer to the question: Why is there not 
a hopeless mixture of pollens? 


134 SCIENCE, OLD AND NEW 


How do the Insects ‘‘Know’’? 


But the next question is: How are insects guided to the 
profitable flowers, or how do they recognize them as 
the flowers they are out to visit on that journey? The 
answers given to this question have been so discrepant, 
some authorities laying emphasis on colour-sense, and 
others on the sense of smell, and others on memories which 
associate certain shapes and textures with abundant 
nectar, and so on, that we are glad to avail ourselves of 
Professor Bouvier’s Psychic Life of Insects (1922), which 
takes a critical survey of the known facts. 

Many observers have concluded that bees pay most 
frequent visits to flowers (or even baited paper) with 
gaudy colours; but there has rarely been any firm dis- 
crimination between colour as such and the brilliance 
of the reflecting surface. What counts for most is con- 
spicuousness against the green background, and bees are 
in some measure colour-blind! Uncovered flowers at- 
tract more visitors than the same flowers next door but 
shaded by leaves; highly coloured flowers with slight 
odour, like dahlias, attract more visitors than their fra- 
grant inconspicuous neighbours, such as mignonette; 
conspicuous flowers get far more visitors than honey in 
a beaker next door. 

The conspicuousness may depend on form and size 
as well as colour, as is shown by the attentions some butter- 
flies pay to the big white flowers of the field convolvulus. 
The visits cease when the corolla is removed, though the 
nectaries remain intact. Yet after some time various 
kinds of insect visitors undoubtedly learn to come to 
honey-flowers whose petals have been cut off. This is a 
very suggestive fact. 

Then there is fragrance, which certainly counts for 
much among hive-bees, for they are very richly endowed 
with smelling hairs. Darwin said that ‘‘bumble-bees 


THE FLOWER AND THE BEE 135 


and honey-bees are good botanists’’ because they recog- 
nize the same kind of flower though the colour is differ- 
ent. They obey the advice of the father of botany: 
“Do not trust too much to colour.” It is probably the 
characteristic perfume, mainly due to the flower’s essential 
oils, that enables the bees to become ‘‘good botanists.” 
Kerner saw a convolvulus hawk-moth fly straight to the 
invisible flowers of a honeysuckle over a hundred yards 
away. For a long range, then, where colour, brilliant 
surface, and shape cannot count as guides, certain insects, 
like bees and moths, may be attracted by odours diffusing 
through the air. When they come near, the other in- 
fluences may tell. On the other hand, a bee attracted 
to a flower by its conspicuousness may turn away when 
it detects the perfume. 


The Role of Learning 


The question of the guidance of insect visitors to use- 
ful flowers has got into some confusion because different 
insects are differently attracted, and different flowers have 
different advertisements. Each case must be studied by 
itself. But there is more than that. Too little attention 
has been given to the capacity insects have of profiting 
by individual experience. They are not altogether in- 
stinctive automata; they are intelligent learners. They 
can attend and they can remember. They can build up 
associations between certain advertisements (colour, 
shape, fragrance), and good meals. Forel showed that 
bees learn to force their way into flowers covered up by 
leaves; Perez showed that bees learn to visit the scarlet 
pelargonium, which they dislike, provided a little honey 
is introduced for a while into the corollas; Bouvier and 
others have shown that hive-bees learn to profit by slits 
and holes which other bees have made as short cuts to 
the nectaries; and many observers have noticed that 


136 SCIENCE, OLD AND NEW 


bees learn to give up visiting flowers which promise well 
but are in reality disappointing. No doubt bees are 
dominated by their hereditary inborn instincts, but we 
fail to make sense of their behaviour unless we also give 
them credit for an intelligent criticism of advertisements. 


XVIII 


THE NATURAL HISTORY OF WAX 


137 





THE NATURAL HISTORY OF WAX 


WAX is not one thing but many, not any longer, they 
say, including sealing-wax. Most familiar is beeswax, 
and it may be said to be almost fundamental to the hive. 
For without the comb of wax it would be difficult to make 
a large store of honey. Wax-making is part of the divi- 
sion of labour within the hive, and it is an extraordinary 
performance. A number of bees take a good meal and 
then hang together in quiet clusters. In eight little 
pockets on the under surface of the hind part of the body 
a somewhat fatty secretion oozes out and hardens into 
a transparent platelet of wax. These fish-scale-like 
platelets project between four of the rings or segments 
of the abdomen. After a while, when the wax-makers are 
going to be comb-builders, they transfer the wax plate- 
lets from the pockets to the mouth, using their feet in so 
doing. The bees then use their jaws to chew the wax, 
and as some air gets entangled in the substance it comes 
about that the transparent wax changes to a more or less 
white colour, just as white of egg does when it is whipped. 
How the bees use this valuable material in building the 
beautiful cells with their tissue-paper-like walls, is familiar 
to all; but it never seems to become less wonderful. Bees 
are not Senior Wranglers, but they are excellent architects. 


Nature and Origin of Beeswax 


What is this beeswax and where did it come from? 
The secretion is a complex mixture. Very important 
139 


140 SCIENCE, OLD AND NEW 


is an ingredient called cerin (cera, wax), soluble in hot 
alcohol and really a fatty acid. Much more abundant, 
up to 85 per cent., is myricin, not soluble in alcohol; it is 
what is called an ‘‘ester,’’ and related to palmitic acid. 
There are hydro-carbons too, related to paraffin, and 
minute quantities of alcohols which the teetotaler cannot 
escape if he eats the honey-comb. We must not forget 
an acid that gives wax its characteristic odour. An 
interesting fact is that the wax made by humble-bees is 
quite different from that made by hive-bees; it consists 
mostly of an alcohol, not of an “‘ester.’’ This illustrates 
what is called ‘‘specificity.” Every animal is itself and 
no other, and this applies to its products, like milk and 
wax, as well as to the creature’s blood and flesh. 

As to the origin of the wax, the answer is clear—the bee 
is a chemical laboratory. The old naturalists, like Réau- 
mur, seem to have thought that bees found wax ready 
made among the flowers, just as they find sugar. But it 
has been proved up to the hilt that bees manufacture wax 
out of their food, and that the sugar of the nectar counts 
for much more than the pollen in wax-production. Wax 
is a by-product of the chemical routine (or metabolism) 
of the bee’s body; and, as in scores of other cases, the by- 
product has come to be a very important factor in life. 
For what would a worker hive-bee do without wax? Of 
course we are not pretending that we or any other biolo- 
gists understand with anything like clearness how bees 
turn sugar into wax. Yet it is something to know that 
this is what they do. 


Wax Made by Other Insects 


But bees are not the only insects that make wax. Thus 
Chinese wax, which has been used for making candles since 
the thirteenth century, is exuded from a coccus insect that 
sucks the sap of the Chinese ash tree and some other plants. 


THE NATURAL HISTORY OF WAX 141 


It consists of a fatty acid (the cerin of beeswax), asso- 
ciated with an alcohol to make an “‘ester.”” Chinese wax 
is a brilliant white, pulverisable, crystalline substance. 
Not very different is the cochineal wax exuded by skin 
glands of the cochineal insect which frequents one of the 
cactuses (Opuntia). The fleshy parts of the cactus may 
be quite covered with a dense crowd of motionless female 
cochineal insects. These are enveloped in a glistening 
white wax in the form of fine threads or particles. The 
males fly about, and are not wax-makers, though the 
cocoons from which they emerged on the cactus are 
mainly composed of this plastic material. If we regard 
femaleness as implying a preponderance of up-building, 
constructive, assimilative, or, in short, anabolic processes, 
whereas the male is relatively on the opposite tack, we 
can understand that only the female cochineal insects 
are wax-makers. Wax is a regularised overflow of ana- 
bolic products. To state the case from the opposite side, 
drone bees do not make wax. 

The oldest sealing-wax was made of beeswax, and its 
obvious value, besides adhesiveness, was in retaining an 
impression for a considerable time. This was replaced by 
shellac, which is produced by the females of another 
coccus insect, apparently as a protective covering. To 
the shellac there were added from time to time various 
adjuncts, and sometimes there are said to be more ad- 
juncts than shellac. But if we understand the matter 
aright shellac is not a true wax. 

In some parts of North Europe the ends of the twigs of 
the alder trees seem to be dusted in summer with white 
powder. When this is scrutinised it is found that the twig 
is covered with young green flies or aphids, like those on 
our rose bushes and bean plants. There are numerous 
glands opening on the insect’s back, and the exudation 
of the secretion forms tiny spine-like prominences which 
make the creature like a miniature porcupine. An in- 


142 SCIENCE, OLD AND NEW 


quisitive naturalist collected over 100,000 of these aphids, 
and had the exudation analysed. It was found to be a true 
wax—mainly consisting of an ‘“‘ester’—and its use 
appears to be that it protects the aphids from the rain, 
for the waxy secretion cannot be wetted! It is interesting 
to find the same sort of by-product being turned to very 
diverse uses; the beeswax forms cups for the honey, 
but in the alder-tree green fly the wax is a waterproof. 


Vegetable Wax 


But there are plant waxes as well as animal waxes; and 
some of the former, like myrtle wax and Japanese wax 
are commercial products just like beeswax. It has been 
noticed that various plants growing in conditions of 
drought have a waxy varnish over their leaves, which 
reduces the loss of water. The experiment of dissolving 
off the waxy varnish has been made; the result was a 
greatly increased loss of water. Some of the blue-gums 
or eucalyptus trees show the waxy exudation very clearly. 
In certain cases the waxiness is seen in the young leaves, 
but disappears later, doubtless for some good physiologi- 
cal reason. But the protection afforded by waxy varnish 
in the young leaves may be effected later on in some other 
way, for instance by an increase in the thickness of the 
cuticle. In general terms we may say that waxiness on 
the surface of leaf and fruit serves to check excessive loss 
of water. 

Everyone knows the little green things in ‘‘caper 
sauce.” They are the flower-buds of a Mediterranean 
shrub (Capparis spinosa), which is of some interest in 
connection with wax. The leaves are from the first 
somewhat waxy on their surface, but as the weather be- 
comes warmer the secretion of wax increases and closes 
up the stomata. For the difficult time of drought the 
caper leaves reduce their loss of water to a minimum. 


THE NATURAL HISTORY OF WAX 143 


No one can think of wax without picturing something of 
the part it has played in human affairs. We think of wax 
forming ancient tablets on which momentous events were 
recorded all too transiently, or making seals for old docu- 
ments that have been charters of freedom, or serving as 
a casting medium for great works of art, or building up 
candles which are beautiful unlit, and still more beauti- 
ful in their burning. 





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XIX 


SHOWERS OF GOSSAMER 


145 





SHOWERS OF GOSSAMER 


AT the Fall of the year the links are sometimes covered 
for long stretches with quivering threads of gossamer. 
On certain slopes there is an almost continuous veil, and 
if one stoops down and looks against the light one sees 
what might well serve as a symbol of the Web of Life 
itself, except that it is not orderly. There is an intricate 
tangle of trembling lines, which cannot be mistaken for 
ground-webs or even for ground snares, for they are 
disconnected and run anyhow. ‘They are never viscid, 
though some may be what Robert Louis Stevenson called 
““dew-bediamonded.’”’ We sometimes see them stretching 
over an acre of ploughed land or veiling many yards of 
hedgerow. Often they float against our face as we walk; 
they catch on our clothes hke long hairs, 


What ts Gossamer? 


On a fine autumn morning, when there is a slight 
breeze, several kinds of small spiders mount on posts 
and palings and tall herbage, and, standing with their 
heads to the wind, emit from their spinnerets a number of 
threads of gossamer. Four is probably the commonest 
number, each issuing from a spinneret with many spin- 
ning spools. We say “‘as fine as gossamer,” but we should 
remember that each thread is the result of the coalescence 
of a multiple jet of liquid silkk. According to the number 

147 


148 SCIENCE, OLD AND NEW 


of spinnerets and spinning-glands used, the thread of 
gossamer will vary in tenuity. 

When the threads paid out become long enough, the 
wind grips them; and when the tug is strong the tip- 
toeing spinner lets go. It is borne on the wings of the 
wind, supported by its silken parachutes, from one parish 
to another, from a crowded'area to a place with more 
elbow-room. In some cases the spider is floated across a 
sheet of water, with the tips of its toes just touching the 
surface film. Usually, we think, the spider is upside 
down—as it is borne through the air. There is no doubt 
that the ballooning is a method of passive migration. It 
is congruent with the autumnal restlessness of many other 
creatures. 


Subtleties of Ballooning 


Careful observers assure us that there is often con- 
siderable subtlety in the ballooning. If the wind falls, the 
floating spider can pay out more silk, just as the sailor 
can unfurl more sail. If the wind rises, the spider can 
coil in part of its thread just as a sailor can take in a reef 
in the ship’s sail. Mr. Blackwell, who wrote a fine mono- 
graph on British Spiders, published by the Ray Society 
about 1860, kept some spiders captive on a branch 
planted in a pot surrounded with a moat of water. He 
noticed that if there was a draught in the room the prison- 
ers took advantage of it and emitted silk threads. If the 
free end of one of these caught on the far side of the moat, 
the spider fixed the near end on a twig and very carefully 
crept across the trembling bridge into freedom. When 
the whole pot was covered with a large bell glass, so that 
there was no draught, then there was no gossamer. It 
seems clear, therefore, that a current of air is necessary 
as the trigger-pulling stimulus of gossamer-making; and 
in natural conditions there is no flight of gossamer unless 
there is a slight breeze. 


SHOWERS OF GOSSAMER 149 


The Shower of Gossamer 


Many of the threads of silk break off at the very start 
and are failures. Other threads are separated off in tran- 
sit by gusts of wind and the like. Others again sink to 
the ground, or against the hedgerow, bearing their spinner 
with them. When thousands of little spiders spin gossa- 
mer some fine autumn morning, a shower of gossamer 
naturally results, but chiefly in the way last mentioned. 
The threads we see on the ground, on the hedge, among 
the grass, are threads that have fulfilled their purpose. 
It is interesting to notice that the essential facts in an 
explanation of a.shower of gossamer were discovered 
more than 200 years ago by a boy of thirteen, Jonathan 
Edwards, who afterwards became famous as a preacher 
of rather terrible sermons and as the author of a treatise 
on the ‘‘Freedom of the Will.” 


Darwin on Gossamer 


When Charles Darwin was on his famous ‘‘Beagle”’ 
voyage round the world—a Columbus voyage in a very 
real sense, for it led to the discovery of a new world—he 
made some interesting observations on gossamer. 

When the ship was sixty miles from land, within the 
mouth of the Plata, the air ‘‘was full of patches of the 
flocculent web, as on an autumnal day in England. Vast 
numbers of a small spider, about one-tenth of an inch in 
length and of a dusky red colour, were attached to the 
webs. There must have been, I should suppose, some 
thousands on the ship.”’ Darwin noticed that the zronauts 
were very active and very thirsty when they arrived on 
board. 

Everyone has heard at least of the Indian Rope Trick. 
Some say that a rope is thrown into the air and that a boy 
climbs up it and disappears. We do not know the facts 


150 SCIENCE, OLD AND NEW 


of the case or their explanation; but we know that spiders 
throw silken threads into the air and sail away on them. 
We know that typically terrestrial creatures, without 
wings, make long journeys through the air. Animals are 
always attempting the apparently impossible and achiev- 
ing it! 





XX 
PEARLS AND PEARLS 



















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PEARLS AND PEARLS 


THERE has often been argument over the question 
whether two things can be the same and yet different! 
The chemists tell us that indigo made artificially in the 
synthetic laboratory is chemically exactly the same as 
indigo made by the plant, and yet there are practical 
men who say that in the results of using the two sub- 
stances there are slight differences. The same remark 
applies to perfumes and drugs which used to be procured 
solely from plants, but are nowadays concocted artifi- 
cially. Chemically, and to all appearance, the artificial 
product and the natural product are the same, and yet 
there are connoisseurs who maintain that there are dis- 
tinct differences, though of a subtle sort. The same 
question rises in regard to adrenalin made artificially 
in the laboratory and adrenalin produced by the supra- 
renal capsules of the animal. 

There are two ways in which there might be slight 
differences between artificial and natural substances 
which have the same chemical composition. In the first 
place, it is certain that the artificial mode of production 
is quite different from the natural mode of production, 
and this may bring about slight differences in the virtues 
of the final result. In the second place, there may be 
infinitesimal traces of by-products associated with the 
naturally formed substances, but absent from the same 
substances made artificially. And everyone knows that 
a very little often goes a long way. 

153 


154 SCIENCE, OLD AND NEW 


This introduction is relevant to the hot discussion of 
recent years concerning the value of undoubtedly fine 
pearls in whose making man has had a hand. They are 
so like the finest pearls obtained from the unaided pearl- 
oyster that even experts are not always able to distin- 
guish the one from the other. To understand the ques- 
tion, which is of great interest, practically as well as | 
theoretically, it is necessary to consider what may be 
called the different grades of pearl-formation. 


Different Grades of Pearl Formation 


Of no importance for our present discussion are the 
entirely artificial pearls—often quite beautiful—which 
are made in various ways, for instance, from the scales of 
fishes. They cannot be confused with any grade of pearl. 
They are frank imitations—very far removed from the 
bewitching balls of opalescent light with which a dusky 
princess used to play solitaire! 

It is characteristic of molluscs that they are able to 
produce from the superficial layer of their skin a shell, 
whose innermost layer consists of nacre or mother-of- 
pearl. The shell is a non-living, non-cellular cuticle, 
made by the underlying living skin. As the mollusc 
grows it is continually adding to the free edge of its shell, 
enlarging its house as it enlarges its body. So it has 
got to moult periodically and begin afresh as is the case 
with crustaceans and other jointed-footed (Arthropod) 
animals. Besides the increase of the mollusc’s shell 
along the margin there is increase in thickness by the 
internal deposition of lamina after lamina of transparent 
lime. Everyone is familiar with the beauty of mother- 
of-pearl on the handles of fruit-knives and the like, and 
it has been known since the days of Sir David Brewster 
that the beauty is due to the physical structure of the 
shell. There is a liquid transparency and a suggestion 


PEARLS AND PEARLS 155 


of rainbow colours, but if you pound a little piece in a 
mortar it is soon a chalky powder with some organic 
matter intermingled. The chemical composition of 
mother-of-pearl differs a little in different parts of the same 
shell, and a good deal in different kinds of molluscs. A 
recent analysis of the nacre of the mother-of-pearl oyster 
(Meleagrina margaritifera) is as follows: Carbonate of 
lime, about 85 per cent.; organic matter, about 12 per 
cent.; and water, about 3 per cent. The organic sub- 
stance which forms the matrix for the lime is called 
conchin or conchiolin, and it also occurs in true pearls. 
The chemical analysis of fine pearls shows a composition 
of about 92 per cent. of carbonate of lime, about 6 per 
cent. of conchin, and about 2 per cent. of water. The 
general similarity between the composition of nacre and 
pearls is of some importance, for the general trend of 
investigation is to show that the finest pearls are connected 
with mother-of-pearl by a series of gradations. 


Imbedded Foreign Objects 


The inside of the pearl-oyster shell is lined by the fold 
of skin called the mantle, and it has been known since 
ancient times that an object intruded between the shell 
and the mantle would become gradually enveloped in fine 
layers of mother-of-pearl. Thus the pearly sarcophagus 
of a little fish is sometimes found soldered to the inside 
of the mother-of-pearl layer; and from ancient days it 
has been the practice to intrude small bodies and retrieve 
them after they have become well covered with nacre. 
A modern improvement on this practice is to drill a hole 
through the shell and insert a rounded fragment of nacre, 
which may serve as a centre for independent deposition 
of fresh material. But there is no possible confusion be- 
tween such imbedding of intruded objects and true 
pearls. 


156 SCIENCE, OLD AND NEW 
True Pearls 


There is a large literature dealing with the natural 
history of pearls, and there is some diversity of opinion 
among experts. But, as it appears to us, the evidence 
adduced by Boutan and others is strong that a true pearl 
is always formed in a sac of skin, which usually encloses 
some irritant or stimulating nucleus. The nature of this 
nucleus varies. It may be a minute grain of sand or 
some other inorganic fragment. It may be the larval 
stage of a fluke or a tapeworm, and then the pearl is the 
sepulchre of an imprisoned parasite! Or it may be a blob 
of organic matter which has not been secreted in a normal 
way. Moreover, it seems that a dimple in the mantle 
may occasionally form a pearl without there being any 
visible nucleus at all. The general features in the making 
of a ‘‘fine pearl” are three—(1) that the seat of formation 
is a sac of the mantle epithelium, quite free from the shell; 
(2) that the cells lining the sac secrete concentric layers 
of carbonate of lime deposited in a framework of conchin 
(as Dubois said, the pearls require both carpenters and 
masons); and (3) that there is usually, though not neces- 
sarily, some visible nucleus which irritates or stimulates 
the walls of the pearl-sac. The fact is that a pearl is a 
nacreous formation occurring under abnormal conditions 
inside the sac of skin. It seems highly probable that the 
walls of the pearl-making sac are in a state of inflamma- 
tion. It would be a mistake, however, to take the pearl 
too seriously as if it indicated a diseased condition. It 
is more comparable to the oak-apple formed on the twig as 
an answer-back to the irritation of the gall-insect. A pearl 
is like an animal gall—a response to something that has gone 
slightly agley. 

Japanese Pearls 


Till a short time ago, the most that man had done in 
the way of provoking the formation of pearls by bivalves, 


PEARLS AND PEARLS 157 


like the mother-of-pearl oyster, was by the introduction 
of small bodies into the mollusc’s skin. When the intro- 
duced body was a nodule of nacre the “‘pearl’’ that was 
formed had considerable merit, though it had not the 
lustre or opalescence of ‘‘the genuine article.’’ But the 
aspect of the case has changed during the last few years 
since the ingenious Japanese experimenter, Mikimoto, 
succeeded in grafting into the skin of the pearl-oyster 
small pieces of the mantle-epithelium itself, with the result 
that pearl-sacs are developed which form pearls of great 
excellence. They are so fine that some experts at least 
cannot pick them out when they are mingled with others 
of entirely natural origin. Why a pearl formed around 
the nucleus of a parasite should be called ‘‘natural’’ 
while one formed around the nucleus of a piece of oyster- 
skin introduced by man is called ‘‘artificial”’ is beyond our 
understanding. But whether the response of the oyster 
to the fluke, or to a blob of organic matter, is finer than 
the response to a tiny fragment of skin ingrafted by man 
is another question. The proof of the pudding is the 
preeing of it, and the proof of the pearl is its lustre. So 
we are brought back to where we began: Can two 
things be the same and yet different? 


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XOX 


THE PASSIONATE PIGEON 


159 


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THE PASSIONATE PIGEON 


PROBABLY no one ever got so near an understanding of 
pigeons as the late Professor C. O. Whitman, of Chicago, 
who devoted a great many years to making their intimate 
acquaintance. He is reported to have said that he did 
not think he could get much nearer the pigeon’s point of 
view without metempsychosis. Unfortunately he died 
without publishing his results, and although his volumin- 
ous notes have been very skilfully edited by Professor 
Oscar Riddle and others (Carnegie Institution of Washing- 
ton, I919), one cannot but miss the welding together which 
Professor Whitman would have effected. We wish to 
refer to the volume dealing with behaviour, edited by 
Professor Harvey A. Carr, and to that part of it which 
deals with courtship. It may be noted that Professor 
Whitman worked not only with varieties of domestic pig- 
eons, but with numerous wild doves, such as the mourning 
dove, the turtle dove, the bronze wing, the wood-pigeon, 
and the passenger pigeon (now extinct). 


Courtship-Behaviour 


Courtship is an early chapter—not always the first 
chapter—in the reproductive cycle of birds. It may be 
preceded, for instance, by the choice of a ‘‘territory”’ on . 
the part of the male, as in the case of some warblers. It 

161 


162 SCIENCE, OLD AND NEW 


implies biologically a heightening of the sex-impulses 
which makes the consummation more certain and more 
successful; but it may also have a psychological signifi- 
cance in binding the mates together by psychical bonds, 
as Mr. Julian Huxley has well illustrated in his fine study 
of the Great Crested Grebe. It is difficult to steer a 
middle course between exaggerating and depreciating 
the psychical side, but we venture to think that the latter 
is the greater danger. It should be noted: (1) that 
snatch sex-unions may occur apart from any courtship 
ceremonial and apart from any subsequent co-operation 
of the parties; and (2) that the courtship does not always 
lead up to sex-union as its immediate climax, for there 
is sometimes a well-defined ‘‘engagement”’ period, as in 
some wild duck. But only in a few birds has the courtship 
been studied as yet with sufficient care—with any- 
thing like the care with which Whitman observed his 
pigeons. 

Everyone understands that the modes of courtship 
among birds are very varied, they include: appeals 
to the sense of hearing (song, twittering, cooing, crowing, 
calling, and even flapping of wings); appeals to the 
sense of sight (displays of plumage and ornaments, of 
agility and grace, rhythmically repeated movements 
such as bowing, curtseying and dancing; and ‘‘sugges- 
tive’? movements, as when the male pigeon jumps right 
over the female; appeals to the sense of touch, as 
when the male chough strokes the female’s head with his 
bill; chasing the female on the ground or in the air, 
or driving her towards the nest; and diverse subtler 
modes, some of which may have a symbolic significance, 
as when the Great Crested Grebes offer water-weed to 
one another; and here might be included the jousting of 
rival males in sight of the females, as in the well-known 
case of Blackcock, where there is much more than a 
display of movements. 


THE PASSIONATE PIGEON 163 


The Impulses in Courtship 


The impulse to sex-activity arises primarily from within, 
hormones from the reproductive organs setting the body 
aflame, but the fire is fanned by the mutual influence of 
the sexes, and it may be made to burn more intensely 
or more quietly according to extrinsic influences, such as 
those of diet and weather. In pigeons the impulses 
usually arise synchronously in the two sexes, but a lack 
of time-keeping may lead to a prolongation of the court- 
ship or to a premature nest-building and egg-laying. 
This illustrates the temporal variations—lengthening of 
one chapter and telescoping of another—that often occur 
among animals and may have led in the past to the origin 
of distinct species, differing from one another like two 
playings of the same tune. 

It is normal for the male bird to take the initiative 
in courtship, but the rule is often broken; and in this 
connection, as well as in regard to the futile mating of two 
hen-birds, it must be noted that the occurrence of ‘‘sex- 
intergrades,” such as very masculine females, is well 
known among pigeons. One cannot help speculating 
whether these relatively abnormal individuals point the 
way to cases like the Red-necked Phalarope of Orkney and 
the Hebrides, where the female conducts the courtship 
while the male, whose plumage is duller, discharges the 
duties of incubation and also takes charge of the young. 
It is very interesting to find in pigeons individual varia- 
tions which are like the initial stages of what has become 
a racial characteristic in the Phalaropes. We get a 
glimpse of evolution at work. 


Courtship of Pigeons 


The subtlety of animal behaviour is well illustrated by 
the courtship of pigeons. It does not last long in any one 


164 SCIENCE, OLD AND NEW 


cycle, but it is the very antithesis of perfunctory. It is 
often like an elaborate ceremonial. Of the items in the 
preliminary behaviour of male pigeons, the editor of 
Professor Whitman’s observations gives the following 
summary—“‘billing or pecking at their own feathers on the 
wings and certain parts of the tail; preening and shaking 
the feathers; elaborate bowing and cooing; going to the 
nest and giving the nest call; approaching the mate; giving 
amorous glances; wagging the wings; lowering the head; 
swelling the neck; raising the wings; raising and spread- 
ing the tail and feathers on the back and rump; alternately 
stamping and striking the feet and wagging the body 
from side to side, and strutting with drooping wings. 
Charging and driving may be resorted to in the courtship. 
The male walks or rushes at the female, holds the head 
high, lowers the wings, exhibits excitement, elevates the 
back, erects the feathers, pecks perfunctorily or petulantly, 
clucks, and gives the driving coo.”’ 

This summary is too much like a composite photograph; 
it blurs the fact that the behaviour is often in a marked 
degree specific for particular kinds of pigeon. Thus the 
mourning-dove (Zenaidura) stamps with his feet before his 
desired mate, and the male Bronze-wing stands on tiptoe, 
lifting first one and then the other foot, raising one side 
of the body and then the other ‘‘in a way to exhibit his 
iridescence in different lights.’’ Particular modes of be- 
haviour marked in courtship may also be exhibited when 
the bird is emotionally excited in other connections, for 
instance by the intrusion of another cock; but the proba- 
bility is that the primary reference of the varied move- 
ments is to mating. Two extremes of interpretation must 
be avoided. On the one hand, it seems indubitable that 
the enamoured male shoots his arrows of desire from a 
definitely bent bow, that he is seeking to arouse first the 
interest and then the excitement of the female. On the 
other hand, it seems certain that the behaviour exhibited 


THE PASSIONATE PIGEON 165 


in the courtship is instinctive and specific for the race. It 
is probably the outcome of a long process of selection in 
the course of which ineffective displays have been sifted 
out. 

So far we have dealt only with preliminaries. As the 
intensity of the courtship increases new elements enter 
into the behaviour. Along with bowing there is billing, 
along with curtseying there is jumping, the male fondles 
or hugs the female’s neck, the male opens his mouth and 
the female thrusts in her beak. This last piece of be- 
haviour is very interesting, for one must remember that 
birds are very thoroughly clothed creatures with little 
touch-surface, and one must also remember that both 
parents feed their young by receiving the nestling’s beak 
in their mouth. As Professor Whitman pointed out, there 
is sometimes among animals an intimate linking of con- 
jugal behaviour and parental behaviour. It is probable 
that the change of reference has been of great evolutionary 
importance. 


Nesting 


The courtship activities in pigeons usually extend over 
a period of seven days, but on the third day or so they 
begin to overlap the nesting activities. Sometimes it is 
the male, sometimes it is the female, who chooses the site; 
and the selection is marked by the bird’s remaining near 
the chosen spot and giving the nesting-call to the mate. 
In most cases the female stays on the nest and works at 
its construction, the male bringing one straw after an- 
other, which is sometimes presented in a very character- 
istic way. In some kinds the straw-collecting like the 
subsequent brooding, is shared equally by the two birds. 
Sometimes the female remains on the nest all the night, 
but shares the brooding duties with her mate during 
the day. We must not, however, pass from the chapter 


166 SCIENCE, OLD AND NEW 


which we have selected, without noting the two important 
points that the sex impulses are suppressed during the 
period of incubation, and that the two birds remain 
faithful to one another throughout that time and for the 
whole breeding season. Exceptions occur, of course, but 
Whitman’s prolonged observations indicate clearly that 
both the suppression referred to and the fidelity must be 
regarded as the rule. 


Preferential Mating 


There seems to be no doubt as to the reality of prefer- 
ential mating in pigeons, for the cock’s elaborate cere- 
monial may be met by persistent hostility and most dis- 
couraging indifference, while, on the other hand, the hen 
may leave one suitor for another who defeats him in a 
tussle. Perhaps the deep significance of it all is to make 
the eventual mating more racially successful by not mak- 
ing it too easy, which is just another way of stating Dar- 
win’s theory. In connection with preference, Professor 
Whitman noticed an interesting point, that the specific 
preferences exhibited by birds at maturity are to a large 
extent acquired, being dependent in part on the social 
environment in which the birds are reared. Young birds 
raised under foster-parents of a different species are very 
apt to prefer a mating with a member of that species to a 
mating with one of their own kind. This is important 
theoretically as an illustration of the way in which the 
mind of the creature is ‘‘made’”’ as well as ‘‘born”’; it is 
also interesting practically since it suggests one of the 
reasons why Professor Whitman was so extraordinarily 
successful in crossing widely separated species of pigeons. 
He recognised the psychological factor. 

What has been said may serve as an illustration of the 
subtlety of behaviour in pigeons, but we must not think 
of them as all-round “‘brainy”’ creatures, or as compara- 


THE PASSIONATE PIGEON 167 


ble, for instance, to dogs. From some standpoints they 
are ‘‘unutterably stupid.” They may fail to recognise 
their own eggs a few inches out of place; they may in- 
jure their young in feeding them; they may cast the 
young bird from the nest along with the empty shells; 
they may incubate day after day on a nest where there 
are not any eggs at all. Yet they are not unintelligent, 
for evidences of a capacity for putting two and two to- 
gether or of learning are not difficult to find. The fact 
seems to be that along certain lines of activity, pigeons 
follow somewhat too trustfully the promptings of instinct, 
and only occasionally ring up the intelligent capacities 
which slumber in the higher reaches of their smooth 
brains. 





Li 


aN 
Was Vanna 


XXII 


THE PROBLEM OF ANTLERS 


169 





THE PROBLEM OF ANTLERS 


OF all the superficial differences between the sexes there 
is none more striking—not even the peacock’s tail—than 
the antlers of the deer. They are restricted to stags with 
the single exception of the reindeer, where they occur 
in both sexes, and it may be that this is an exception that 
proves the rule, for in the great majority of cases the 
antlers of the female reindeer are much smaller than those 
of the male. It is possible that reindeer represent an 
exaggeration of a primitive condition in which small 
antlers were common to both sexes, as horns are in cattle. 
Or it may be, as others would say, that reindeer show 
us an interesting phase of evolution where distinctively 
masculine characters, originally sex-linked, are being 
transferred to the female as well. It is possible that the 
antlers in reindeer have some every-day use, common to 
both sexes, but the evidence on this point is discrepant. 


An Expensive Decoration 


From an economic and social point of view many pre- 
fer sheep-pasture to deer-forest, but it is impossible to 
refuse to admit a zoological and esthetic thrill when we 
see a fine stag on the sky-line, with a magnificent set of 
antlers standing out as if in defiant declaration that every- 
thing is not utilitarian. For this is one of the problems 
that antlers present; they are very expensive structures 


171 


172 SCIENCE, OLD AND NEW 


and yet we are not sure that they are of any use. They 
represent a lavish expenditure of organic material; they 
may weigh over seventy pounds; they form an encum- 
brance on the stately head; they have to be made afresh 
. each season; they leave a red, raw patch when they fall 
off. It is by no means clear that they make effective 
weapons when stag fights with stag; they sometimes be- 
come entangled so that death conquers both combatants. 
If a stag that has lost his antlers is forced to fight during 
the ten days or so before the new ones begin to grow, he 
can give a good account of himself with fore-hoofs and 
teeth. In spite of fine pictures it does not appear that 
antlers are good weapons when a stag stands at bay against 
a pack of wolves. The usual answer is, of course, the 
Darwinian one—that the stags with the best antlers 
secure the largest harems, partly by their success in 
driving away rivals and partly by their conquests in an- 
other direction. But while we are not inclined to with- 
draw adherence from this theory, we must admit that 
there are some difficulties in its way. Thus aberrant 
hornless stags sometimes have a following of wives more 
numerous than their normally equipped rivals have been 
able to secure. 

In view of these and other difficulties, it has been sug- 
gested by Mr. Mortimer Batten that the real use of the 
antlers is to make the stags conspicuous, thus drawing 
attention away from the hinds. If this could be sub- 
stantiated it would be, we think, a unique case that one 
sex should have a character, disadvantageous to itself, 
yet established by natural selection because it secures 
the safety of the other. 


Masculine Exuberance 


We venture to suggest that all these theories are more 
or less wrong, and that antlers are exuberant outcrops 


THE PROBLEM OF ANTLERS 173 


of the male constitution, of no particular use except in so 
far as they enhance the tout ensemble impression which 
excites the sex-interest of the females. To that end, how- 
ever, they are at most accessory; their primary signifi- 
cance is as exaggerated expressions of virility, apt to 
transcend the limit of safety. For it is highly probable 
that they contributed to the disappearance of the giant 
Trish deer. Perhaps antlers have their counterpart in 
the huge, six feet long, spear-like tooth of the male Nar- 
whal, for which again, no definite use is known. 


Development of Antlers 


The problem of antlers deepens when we inquire into 
their development, following a very striking investiga- 
tion by the famous Glasgow surgeon, Sir William Mac- 
Ewen (The Growth and Shedding of the Antlers of the Deer, 
1920). In a buck’s first year an outgrowth, or pedicle, 
rises from the frontal bone. This is a permanent struc- 
ture which grows in girth during subsequent years. 
From the summit of the pedicle the antler grows in the 
second year, as the result of an extraordinarily rapid 
multiplication of bone-forming cells (osteoblasts), which 
extract lime from the blood and immure themselves into 
hard tissue. There is no bone-mending or bone-regrowth 
so rapid as the development of antlers. ‘‘The rapidity 
of growth in the antler is comparable with, but in excess 
of, that of the most rapidly produced tumours,” and 
according to Professor MacEwen the multiplication of 
cells that goes on at the base of the antler is accomplished 
by a peculiar process of nuclear budding (an adjunct to the 
ordinary methods of cell-division). It is very interest- 
ing to find that ‘‘a somewhat similar process to nuclear 
budding in the antler is seen in rapidly-growing tumours, 
such as the sarcomata.” This suggests that antler- 


174 SCIENCE, OLD AND NEW 


formation may be interpreted as a semi-pathological 
process which has become more or less normalised. 

The pedicle grows out in the first year, the antler ap- 
pears in the second year, and the first antler has only 
a single stem. The second antler has a stem and one 
branch or tine, and everyone knows that a new tine is 
added each succeeding year until maturity is reached, 
after which the growth becomes irregular. 

Before a new antler begins to grow there is a greatly in- 
creased blood-supply in the skull and in the permanent 
pedicle. When growth begins there is, as it were, an 
overflow of cartilage and young bone from the upper 
surface of the pedicle—‘‘in form like a young mushroom 
projecting from its stalk.’ The cartilage grows out dis- 
tally, leading the way, while proximally, next the pedicle, 
it turns into the bone of the antler. ‘‘The more it con- 
tributes to the growth of bone, the farther it is borne away 
from the centre by the osseous deposit which it has so 
freely furnished.” According to MacEwen the bone of 
the antler is usually formed indirectly through the inter- 
mediation of a cartilage or gristle phase, but direct bone- 
formation may also occur in the tines. 

Meanwhile, as the antler continues sprouting, the skin 
is carried upwards with it, forming the hot, short-haired 
“‘velvet,’’ rich in blood-vessels. It is an extraordinary 
phenomenon, this yearly extension of skin over a large 
surface in the course of the three months when the antler 
is a-forming. Outside embryonic development we cannot 
find anything approaching it except in cases where a 
newt replaces a considerable part of a lost leg, or a lizard 
most of its surrendered tail. There are numerous big 
blood-vessels in the velvet, supplying the food that admits 
of its rapid extension, and also keeping the growing 
antler-tissue suitably warm. The materials for the growth 
of the antler itself are brought by internal. blood-vessels 
from the pedicle or stalk. It may be noted that ridge- 


THE PROBLEM OF ANTLERS 175 


like outgrowths from the surface of the antler form 
grooves or gutters in which the skin-vessels lie, and that 
there may be a sparse interlinking of the deeper branches 
of the superficial blood-vessels with the network of thin- 
walled vessels in the interior of the antler itself. Branches 
of the Fifth or Trigeminal nerve from the brain run up the 
velvet, and make it exquisitely sensitive—another adap- 
tation, for it saves the stag from knocking the still soft 
antlers against hard objects. The sensitiveness of the 
skin usually saves the growing antler from deformity, 
but it should be recognised that so long as the antler is 
actively growing it can within limits repair itself. 


The Shedding of the Antlers 


Perhaps the most extraordinary fact about antlers is 
that they should be shed. In a few cases, as among the 
Sambar Deer of the Far East, the antlers are shed at 
intervals of a few years, but in ordinary deer the huge 
structures are as transient as the leaves on the tree. 
Those of the Red Deer are usually dropped about Febru- 
ary, and even the stag himself seems a little surprised! 
There is no doubt that they are often gnawed after 
they fall. As to the actual shedding, Sir William Mac- 
Ewen tells us much that is full of interest. ‘‘At the birth 
of the new antler, provision for its ultimate separation is 
already foreshadowed, and preparation for its shedding 
may be seen during the period of its most vigorous 
growth.” At the very outset the material that sprouts 
from the pedicle of the antler overflows and forms a pro- 
jecting ring, afterwards called the corona, and about the 
level of this ring there occur the essential changes that 
bring about shedding. The edge of the corona, growing 
outwards, puts the skin and the superficial blood-vessels 
on the stretch, so that they eventually give way. This 
means cutting off the blood-supply of the velvet, which 


176 SCIENCE, OLD AND NEW 


dries, shrivels and peels off in shreds. Meanwhile, the 
bone-cells of the antler at the level of the corona multiply; 
they crowd, constrict and obliterate the internal blood- 
vessels, and an ivory-like barrier is formed which makes 
the antler dead tissue. But there is a third step, which is 
taken by the living tissue at the top of the pedicle. A 
soft granulation tissue is formed which gradually loosens 
the organic connections between the pedicle and the 
dead antler. This soft granulation tissue, which aids in the 
floating-off or sloughing-off of the antler, also furnishes 
material for the growth of its successor. There are crowds 
of osteoblasts, ready to begin their labours of bone-form- 
ing. As a final adaptation, it may be noted that the 
granulation tissue forming on the surface of the pedicle 
prior to shedding will tend to exclude germs and prevent 
suppuration, though that may occasionally occur. 


The Puzzles that Remain 


Can one understand the apparent wastefulness of the 
shedding of the antlers? Will it do to say that from the 
manner in which antlers are constructed they must be 
shed if a larger set is to be secured next year? Will it do 
to say that the manner in which antlers are constructed 
involves a dying away of tissue which might become a 
dangerous process zf it spread? It is safer that the whole 
of the fine structure should be jettisoned. But we do not 
know. 

We doubt if there are any ‘‘side-shows”’ in the animal 
kingdom more remarkable than this growth and shedding 
of antlers. The growth is so rapid and expensive, the re- 
sult is so transient and superfluous. The potentiality 
which is part of the inheritance is actualised under the 
influence of hormones (chemical messengers) from the 
reproductive organs, and (excluding reindeer) the poten- 
tiality will not normally come to anything except in 


THE PROBLEM OF ANTLERS 177 


masculine soil. Disturbances in the sex-life are often 
registered in abnormalities of the antlers, and, indeed, the 
whole story of antlers reads like a commentary on the 
biological expensiveness of sex. Then there is the sugges- 
tion that the growth of the antler has its counterpart in 
the abnormal growth of a tumour, and there is no doubt, 
at any rate, that the necrosis natural in the shedding of the 
stag’s antler would be pathological elsewhere. Most 
striking of all, perhaps, is Sir William MacEwen’s dis- 
tinctive discovery of the preparations that are made 
from the very beginning of the antler’s life for the shed- 
ding which is its end. It does not seem easy to get away 
from organic teleology! 





XXITI 


DANCING AMONG BIRDS AND BEASTS 


179 





DANCING AMONG BIRDS AND BEASTS 


WE are not thinking of oddities like the dancing mouse, 
nor of pathetic creatures, like captive bears, which have 
been taught by man to “‘dance.’”’ What we have in mind 
are various animals, at different levels of organisation, 
which show off before their desired mates with an abandon 
of movements, sometimes rhythmic and almost always 
graceful, for which dancing seems the only word. 

Thus, in the courting redshanks, Mr. Edmund Selous 
has told us how the male waves and flutters his wings 
above his back, nervously moving his coral-red legs, and 
uttering a little tremulous note. As a matter of fact, he 
is rather behind than in front of his desired mate, but the 
slightest turn of her restless head enables her to keep 
him in view. Of course, until or unless her interest is 
aroused the cock’s dancing is of no use at all. 


Dancing Ruffs 


A similar absence of elaborateness is illustrated by the 
ruffs, which do so much in the way of mock-fighting. 
Mr. Selous writes: ‘“‘Birds dart like lightning over the 
ground, turn, crouch, dart again, ruffle about each demure- 
looking, unperturbed little attraction, spring at each 
other, and then, as though earth were inadequate as a me- 
dium of emotional expression, rise into the air and dart 
around overhead, on the wing.” The ruff darts at the 

181 


182 SCIENCE, OLD AND NEW 


reeve, rebounds from her, darts back again, expands his 
collar, droops his wing, ‘‘as though he would overwhelm 
her with his gallant show, but then sinks prostrate at her 
side, and remains thus glued to the earth.’”’ Unless Na- 
ture is magical there is a high tide of emotion, as well as 
of bodily excitement. 

Very striking are the descriptions given of the behaviour 
of the South American cock-of-the-rock, where one suitor 
after another shows off before a gallery of spectators. 
A clear arena is chosen and there the candidate, with 
orange-scarlet crest and plumage, dances a minuet, 
spreading his wings and tail. ‘‘Finally,” says the late 
Mr. W. H. Hudson, ‘‘carried away with excitement, he 
leaps and gyrates in the most astonishing manner, until, 
becoming exhausted, he retires and another bird takes 
his place.”’ In this case a somewhat subtle note is struck, 
anticipating certain native dances in which only one 
person performs at a time. There is a social and com- 
petitive aspect. 


Joy-Dances 


In his** Naturalist in.La Plata,’ the late: MroWaE 
Hudson, of evergreen memory, gave a number of examples 
of dancing among birds. His interpretation differed 
somewhat from Darwin’s, for he felt bound to conclude 
that in many cases the dance was not the cock’s competi- 
tive display of good points, nor his endeavour to excite 
and rivet the hen-bird’s attention, but was rather an ex- 
pression of joie de vivre and exuberant vigour. An over- 
flow of joyousness in high-strung creatures will naturally 
find artistic expression and racial individuality. Emotion 
and motion become closely linked. On the other hand, 
artistic expression at any level is very often useful, and 
from observations like those of Mr. Selous, and from 
what we have seen for ourselves, we are inclined to regard 


DANCING AMONG BIRDS AND BEASTS _ 183 


Mr. Hudson’s interpretation simply as a supplement to 
the Darwinian one, that the male’s dance, like his song, is 
an expression of lust and love—the ever-intermingled 
clay and gold—and is useful in exciting and focusing 
the desired mate’s interest. In some cases the best 
reward will be given to the male who deserves it most. 
And that is always well. 


Transcending Sex 


But there is good reason to believe that among animals 
—as certainly in man—activities which were at first 
directly linked to sex may transcend the fleshly trammels 
and acquire a new significance. Thus the voice, primarily 
a sex-call, becomes an instrument of reasonable discourse 
or a medium of purely esthetic emotion. And it seems 
to us that this transmutation is hinted at in some of Mr. 
Hudson’s cases. Thus he tells us of the singularly wattled, 
wing-spurred, long-toed jacanas that a flock of them will 
suddenly, in response to a note of invitation, leave off 
feeding and fly to one spot, where they form a close 
cluster and indulge in a strange display, both sexes taking 
part. They spread out their wings, “‘like beautiful flags 
grouped closely together; some hold the wings up verti- 
cally and motionless; others, half open and vibrating 
rapidly; while still others wave them up and down with 
a slow, measured beat.” 

Still stranger is the spur-winged lapwing’s performance, 
which occurs all the year round, either by day or in the 
light of the moon. Two members of a pair—a married 
couple in other words—are joined by a third plover, the 
husband of another spouse. They welcome his presence 
‘‘with notes and signs of pleasure.’’ Of course, it is very 
difficult for us to get mentally near these creatures! Is 
this a friendly decorous visit, an old friend, perhaps a 
brother, coming to call on the married couple? Or is 


184 SCIENCE, OLD AND NEW 


number three a seducer coveting his neighbour’s wife; 
or is he welcomed because he fans the fires of waning con- 
jugal affection? Or is it just what Scots folks call a ‘‘di- 
version,’’ nearer to play than to anything else? In any 
case it is artistic. Advancing to the visitor, the husband 
and wife place themselves behind him. ‘‘Then all three, 
keeping step, begin a rapid march, uttering resonant 
drumming notes in time with their movements. The 
march ceases: the (visitor) leader elevates his wings and 
stands erect and motionless, still uttering loud notes; 
while the other two, with puffed-out plumage and standing 
exactly abreast, stoop forward and downward until the 
tips of their beaks touch the ground, and, sinking their 
rhythmical voices to a murmur, remain for some time in 
this posture. The performance is then over and the visitor 
goes back to his own ground and mate, to receive himself 
a visitor later on.” The data are obviously insufficient 
for scientific judgment, but it seems clear that animal 
behaviour is subtler than many people think. 


The Dance of Spiders 


It is well known that the courtship of spiders is in many 
cases very remarkable. The male is often a pigmy com- 
pared with the female; his advances are made with cau- 
tion, for her temper is very uncertain. In the family 
of garden-spiders the courting is to some extent carried 
on by vibrating certain lines of the web—a method which 
has the advantage of leaving a way of retreat open. The 
males sometimes engage in mock-fights, and, like the 
ruffs, they do not hurt one another. In other cases what 
is most developed is a kind of dance. The male poses so 
that he displays his good points in the eyes of the short- 
sighted female, and may describe a semicircle before 
her, to and fro, many times. Or he may whirl madly 
round her until her coyness breaks down and she joins in 


DANCING AMONG BIRDS AND BEASTS _ 185 


the dance. In one case the Peckhams counted one hundred 
and eleven circles made by the ardent male. In spite of his 
care the courtship is often fatal to the suitor, for the female 
may rush at him and end the dance with his death. The 
Peckhams write: ‘‘The female of Dendryphantes elegans 
is much larger than the male, and her loveliness is accom- 
panied by an extreme irritability of temper, which the 
male seems to regard as a constant menace to his safety: 
but his eagerness being great, and his manners devoted 
and tender, he gradually overcomes her opposition.’’ In 
the case of spiders, it appears highly probable that the 
courtship-dance serves to excite the interest and sex- 
instincts of the female, but she always remains more 
than a little ‘‘difficult.”’ 


Indian Ocean Calling-Crab 


The Indian Ocean calling-crab disports himself before 
his mate on the shore, brandishing his brilliantly-coloured 
right claw, which is exaggerated out of all proportion. 
It is a far cry from this to the strutting and parade of 
peacock and pheasant, Argus and Tragopan, or to the 
more dance-like aérial displays of Birds of Paradise and 
humming birds; but throughout there is surely a touch 
of Nature that makes the whole world kin, and does not 
leave human dances out. Emotion expressed in rhythmic 
motion is common to all, but the gamut is a long one. 


enn’ od OO Ra 9 An oo. ene ee A, 
BUC ye a) RR NY ae wee fatiew 
i ao v w% ? I ba , 


he i in Rh oe An i. yan 





XXIV 


MOTHERING AMONG ANIMALS 


187 





MOTHERING AMONG ANIMALS 


WHEN we sit among the heather on a summer holiday 
we sometimes see a mother-spider hurrying through the 
jungle with a silk ball on her breast. That tiny ball, 
about the size of a pill, is a portable cradle; it contains 
the eggs and by and by the spiderlings. The mother- 
spider is very careful of it; if you are hard-hearted enough 
to take it from her for a little she will search for it dili- 
gently. For its sake she will risk her own life. Now this 
sounds a note which we hear all through the animal 
kingdom—the note of mothering. Sometimes clearly, 
sometimes dully, sometimes high-pitched, sometimes low- 
pitched, this maternal note is sounded—not universally, 
we admit, but very frequently. A cod-fish may produce 
two million eggs which are liberated into the universal 
cradle of the sea, and in such cases there can be no ques- 
tion of parental care. It is neither possible nor necessary 
when theres that superabundant multiplication which we 
call ‘“‘spawning.” The mother frog lays her thousand 
or three thousand eggs in the shallows of the pond, but 
she takes no care of the tadpoles. In these cases there 
is usually a prodigious infantile mortality, and the race 
continues because there are so many. One of the star- 
fishes, called Luidia, is said to produce two hundred mil- 
lion eggs in a year, and yet it is not a common animal. 
It is not given to every creature to be so productive as 
this, and in the course of ages all sorts of animals have 

189 


190 SCIENCE, OLD AND NEW 


discovered a better way—to have fewer offspring and to 
take more care of them. So there have evolved many 
different forms of ‘‘mothering.”’ 


Many Forms of Maternal Care 


We pictured the spider carrying about its silken bag of 
eggs, and does that not lead us to think of much higher 
animals where the young ones are carried about by their 
mother, both before and after birth? The kangaroo 
places her very helpless new-born babies in an outside 
skin-pocket developed round the milk glands and squirts 
milk into their mouths, for they cannot even suck! The 
tree opossum, that has no pouch, carries her family on 
her back with their tails curled round her tail. But they 
need to hold on tight when she jumps. The mother-bat 
carries her baby on her breast as she flies through the 
air, and this, it must be admitted, is a great achievement. 
The baby holds on with its thumb and also with its front 
teeth, which are specially suited for gripping the rough 
hair. We have all seen a cat shifting her kittens to what 
she thought was a safer place, and the same is seen among 
wild animals. The mother-squirrel shifts her family from 
a threatened tree, and the hare carries her leverets from 
one place to another when the fox is beginning to find 
out where she lives. 

It is very interesting to notice how nearly related ani- 
mals solve the same problem in different ways. The hare 
and the rabbit are first cousins; but the rabbit makes 
a bed of fur in the far end of the burrow and there brings 
forth blind and naked young ones, while the hare rests in 
an open ‘“‘form” and brings forth furred young ones with 
open eyes. The rabbit’s young are fairly safe because 
they are born in a burrow; the hare’s young are fairly 
safe because the mother is so alert. What the country 
folk say, that she sleeps with her eyes open is true in idea, 


MOTHERING AMONG ANIMALS 191 


though not in fact. It is the same with a human mother 
that when she sleeps, her ear remains awake to the in- 
fant’s cry. How clever too is the hare’s trick of taking a 
flying jump of several feet out of and on to the ‘“‘form,”’ 
so that the scent is broken and the fox is baffled. 


Nests 


The squirrel makes a big nest of moss and twigs on the 
branches of a tree; the harvest mouse weaves strips of 
leaves into a nest fastened to the haulms of wheat; the 
dormouse builds a nest with moss and fibres in a low 
bush in the thicket. Whenever we say the word ‘‘nest”’ 
what a crowd of pictures we see—the stickleback’s nest 
among the water weed, the lamprey’s stone nest in the bed 
of the river, the wasp’s nest hanging from a branch, the 
humble-bee’s nest in a mossy bank, and half a hundred 
more. And it always means mothering. 

But the climax is, of course, among birds. Think of the 
weaver-bird’s nest dangling from the tip of a branch 
overhanging a stream; the rook’s nest swaying on the top- 
most branches of the tree; the sea-swallow’s nest made of 
the consolidated juice of the mouth and glued on the 
side of a precipitous cliff; the nest of the thrush, so well 
plastered within and so well woven without; the two- 
roomed clay nest of the South American oven-bird—a 
hard structure as big as one’s head; the beautiful feather- 
nest of the eider duck made of down from the bird’s own 
body; and the nest of the Long-tailed tit made of over 
two thousand feathers which the bird has individually 
gathered. What industry, what skill, what patience—and 
not for self! 

There is much more than nest-making to be thought of. 
There is the long patience of brooding during hot days 
and cold nights; there is the hard work of feeding the 
nestlings and the need sometimes to stand between them 


192 SCIENCE, OLD AND NEW 


and the sun or to ward off some living enemy; there is the. 
protection of the youngsters when they become restless; 
and there is all the labour of instructing them in the art 
of life. Of course it is the meat and drink of the parents 
to do this for their offspring, but that does not lessen 
our admiration of the other-regarding impulses which 
are often strong enough to lead to a sublime self-forget- 
fulness. 


Teaching the Young 


Too little attention has been given to the amount of 
instruction which many birds and mammals give to their 
children. Take the otter, for instance, we know that the 
mother takes no end of trouble in schooling the cubs. 
She teaches them the A B C of woodcraft, e.g., the sounds 
that are trivial and those that are significant for good or 
ill. She teaches them how to swim without noise and how 
to dive without a splash. She teaches them how to guddle 
for trout, how to dive full fathoms five after plaice, how 
to catch a young rabbit one day and a frog the next. She 
teaches them how to eat the various items on the otter’s 
long bill of fare; how to get home without retracing their 
steps; how to lie perdu underneath the river bank while 
the enemy is searching all around. Surely all this mother- 
ing plays no small part in securing the otter’s survival. 
And she joins in their games till they say good-bye! 


The Ladder of Love 


When we lift a stone from the shallows of a river and 
turn it upside down, we often find two or three leeches, 
some of them with exquisite markings. If we repress an 
absurd prejudice and turn the leeches upside down, we 
frequently find that some of them are carrying their 


MOTHERING AMONG ANIMALS 193 


family about with them. This is parental care in very 
simple expression, and we must not embellish it with 
big words. We know, indeed, almost nothing about the 
leech’s mind. We know, however, that the green sea- 
leech places its eggs in an empty shell and mounts guard 
over them, keeping them clean too, for many weeks, 
without apparently breaking its fast all the time. 

Very common on the seashore are little sandhopperish 
crustaceans, Gammarids by name, which clean up every 
thing. They are unattractive to dull eyes, though they 
wriggle about sideways in a charming manner. The male 
carries the female about with him for a long time—a 
peculiarity not well understood. Now if you take a num- 
ber of these little creatures in a saucer of sea-water, and 
leave them alone, you will see, in the summer time, a pretty 
sight. From beneath the shelter of the mother there issue 
forth many young ones, miniatures of their mother. They 
begin to explore round about, but—there, you have 
jarred the table and they have all taken refuge beneath 
their mother, as chickens under the hen’s wings. Thisis on 
a higher level than the parental care of the brook-leeches, 
but it is on a low level compared with the patience of the 
nesting and brooding bird, compared with the almost 
human mothering that the otter lavishes on her children. 
There is intelligent mothering, and instinctive mothering, 
and there is a mixture of the two. There is also mothering 
so simple that we can only call it mothering. But the big 
fact is this, that at all levels of the animal kingdom, and 
through great reaches of it, there is abundant and gener- 
ous mothering. We hear far too much about the un- 
doubted success that rewards sharp teeth and talons, far 
too little about the undoubted success that rewards good 
mothering. Both are facts—but we hear tao little of the 
latter. Perhaps only naturalists know how much of the 
time and energy of many different kinds of animals is 
devoted to ends which are race-preserving rather than 


194 SCIENCE, OLD AND NEW 


self-preserving, to endeavours which are for others rather 
than for self. 

There are good human reasons for being gentle and 
kind, as well as for being strong and courageous; but there 
is a certain satisfaction in discovering that in the history 
of Animate Nature both have had their reward. Mother- 
care has made it possible for the animal to free its life 
from the burden of enormous families, and it has given 
the youngsters a better send-off on their adventurous 
journey. It has also enriched the life of the parents to 
have children not too numerous to be known and loved. 
And if this be true for animals, how infinitely more for 
mankind. 


XXV 


MILK 


195 


cae 
AL Hi , 





MILK 


Ir was at Harry Lauder’s long ago, when the minstrel 
spoke of meeting a man and going round the corner ‘‘to 
have a drink.” ‘‘A drink o’ milk,” he explained; and 
some man in the audience laughed incontinently. ‘‘Ay,” 
said the genius, ‘‘a drink o’ milk, I was sayin’. And it was 
the first drink you had, my man.” As the audience 
cheered the sally, the minstrel had his victim once again: 
““And may be it’ll be the last drink, too, that you’ll hae.”’ 
From the vita minima of the new-born to the vita minima 
of the moribund—milk! 


An Extraordinary Fluid 


It is certainly one of the most extraordinary of all fluids, 
containing all the three kinds of food, proteins, fats 
and sugar, with water and salts thrown in. In cow’s milk 
there is 3—4 per cent. of protein, 4 of fats, 4.4 of sugar, 
0.6 of salts, and the rest water. One of the interesting 
features is the specificity of milk, for the dolphin’s has 
43.8 per cent. of fat, the reindeer’s 17.2 and the rabbit’s 
16.7. The reindeer’s milk has 10.4 of proteins, the 
dolphin’s 7.6, the camel’s 4, ass’s milk has 5.7 per cent. 
of sugar, goat’s 4.9, and reindeer’s 2.8 per cent. This 
diversity of composition is related, of course, to biological 
conditions; thus the young reindeer in a cold climate re- 
quires a lot of fat; and the young rabbit that doubles 


197 


198 SCIENCE, OLD AND NEW 


its weight in six days after birth requires much more 
nutritious milk than the human baby, who takes 180 days 
to accomplish the same feat. As the baby dolphin is born 
and suckled in the sea, it probably requires all the extra- 
ordinary proportion of fat which we have just noted in the 
composition of its milk. One of the big facts of life is 
specificity; down into details every organism is itself 
and no other. The blood-crystals of a donkey are different 
from those of a horse, and goat’s milk is quite different 
from sheep’s. 


Adapted to Special Needs 


Another big fact of life is adaptation; at every corner 
we meet a fitness. One does not, indeed, make any 
special marvel over the fact that the dolphin, which goes 
in for blubber-making like all other cetaceans, should 
have much fat in its milk. For the milk is a product 
of secretory cells that get their raw materials from the 
blood and the lymph; and if the dolphins have a pre- 
disposition in the way of fat-production, it is quite natural 
that it should show in the milk. At the same time, the 
fattiness of the dolphin’s milk fits in very well. And 
speaking of adaptations, we are reminded that the first 
milk the new-born mammal gets for a short time after 
birth is quite different from the ordinary milk. It is much 
richer in proteins, and has much more cellular débris; 
one would think it must be very useful at the critical 
transition from ante-natal symbiosis to babyhood. No 
doubt there are physiological reasons for it, but it fits in 
very well, does it not? 


Natural History of Milk 


There are many very interesting Natural History facts 
about milk. It is of course a prerogative of mammals 


MILK 199 


to give milk, for ‘‘pigeon’s milk” does not count, not being 
a secretion. It is Nature’s way to make a new thing out 
of an older thing, and the milk-glands are specialisations 
of more ordinary skin glands, like the sebaceous glands 
that keep the fur sleek or the sweat glands that get rid 
of saltish water. In the two egg-laying mammals the 
milk-glands are very peculiar, and one view is that they 
are nearer the sweat-gland type, while those of other 
mammals are nearer the sebaceous type. In these two 
primitive mammals—the Duckmole and the Spiny Ant- 
eater—the ancestral reptile still lurks; and it is very in- 
teresting to find that the young one simply licks a patch 
on its mother’s skin where the secretion exudes by numer- 
ous pores. There are no mamme to suck. Only in the 
case of the Spiny Ant-eater has the ‘‘milk”’ been studied 
carefully. It is very rich in proteins; it has little or no 
sugar; it has no phosphate salts. It is very different from 
ordinary milk. 

We must refrain from describing how the marsupial 
mother forces the milk into the mouth of its offspring 
and yet does not drown it; or how the whale, suckling in 
the sea, gives its huge baby a big mouthful at once. We 
must not linger, for there is a more urgent story to tell. 

Apart from monotremes, which we do not know enough 
about, all young mammals are suckled on milk, and they 
get plenty of it. A puppy doubles its weight in nine days, 
a lamb in fifteen, and in these cases the milk is much 
richer in protein and fatty material than is the milk sup- 
plied to the calf, which grows much more slowly. This 
is the kind of fact that is interesting to the biologist, 
but it becomes of commanding importance when the 
question is of the supply of milk to children. It has been 
demonstrated that children in Great Britain, for instance, 
do not get nearly enough of fresh milk, and the practical 
questions that arise are how they can get more, how the 
quality of what they get can be maintained or improved 


200 SCIENCE, OLD AND NEW 


and whether there are any substitutes which can make up 
for the deficiency. These questions are far beyond our 
province, but there is a general biological question be- 
hind them, namely, what is there about milk that gives 
it such pre-eminence as a food for tender years? 


Why Pre-eminent as Food for the Young? 


Part of the answer is easy and part of it is difficult. 
Mammals have succeeded above all other creatures for 
a variety of reasons—and one of these reasons is milk. 
For this fluid is a handy form of food, available whenever 
the mother is get-at-able; it is readily digestible and 
eminently well suited for gastric education. The young 
fox or stoat or weasel must suck milk for many days be- 
fore it is able to make anything of even prepared flesh, 
such as the mother brings it in due season. A young 
mammal is often very far advanced at birth, especially 
if it is born in conditions where it must live facing risks; 
it is a clamant creature with large needs; how are these 
to be met? The appropriate food is often unprocurable 
except after an apprenticeship to woodcraft, and that 
takes time; so milk fills the gap. But the suckling period 
is often very hazardous at the best, and thus we see the 
value of hurrying on the post-natal growth, which milk 
seems to be pre-eminently capable of doing. Even if the 
critic should say that eating grass does not require much ap- 
prenticeship, it would be fair to reply that grass is not an 
easily digested food, and, so far as we know, the cellulose 
is not digested at all in backboned animals, but is broken 
down into sugars by a whole army of bacteria. We do not 
suppose that the lamb is born with this army. So it must 
suck milk. 

We must get into closer grips with the question, Why is 
milk such a valuable food for tender years? Milk contains 
proteins, such as casein, and proteins are the only kinds 


MILK 201 


of food that afford materials for building-up and sustain- 
ing the living tissues of the body. But all proteins are not 
the same; some are much more valuable for growth and 
repair than others are. It has been shown that milk pro- 
teins are the very best that young mammals can get; 
63 parts per cent. are retained for growth; whereas of 
wheat-protein, only 25 per cent. can be utilised for this 
purpose. Surplus protein material can hardly be said to 
be storable, unless as part of the living tissue. Therefore, 
a daily supply of protein food is essential. 

Then there is milk-sugar, which supplies energy for 
muscular activity and heat for maintaining the tempera- 
ture of the body. This animal heat is necessary if the 
chemical processes are to go on smoothly and at the proper 
rate. The milk-sugar that is not at once used up can be 
stored in the form of animal starch or fat. 

Then there is the fat of the milk, which again affords 
an indispensable supply of energy for muscular activity 
and of heat to maintain the body temperature. The fat, 
as everyone knows, is storable. The salts in the milk 
are essential for bone-making and also for keeping up a 
proper balance in the fluids of the body. Finally, the 
milk includes several accessory food factors or vitamins, 
mysterious substances or properties which are indispen- 
sable to health. It is plain, then, that milk is a perfect 
food, and as grown men can get good substitutes for it, 
they should leave it, when it is scarce, for those who cannot 
—for babes in particular. 


‘ae AARP ny tei ake ect ' 
Be hes . pan iene Hath aaa! 
: we wr aT AS ae a ay i AM Ru ube 


Pare ty PASINGT eT), oe \ 





XXVI 


COMMENSALISM 


203 





COMMENSALISM 


MAny animals live as encrustations on other animals— 
epizoic they may be called. Acorn-shells and worm-tubes 
may be seen growing on a crab’s shell and a zoophyte even 
ona fish. One of the strangest cases is that of a big bunch 
of barnacles fixed to the tail of a sea-snake. Sometimes 
the encrustations become so heavy that they seriously 
handicap their bearer, sometimes they serve as a mask, but 
in most cases the epizoic growths have neither a harmful 
nor a beneficial significance. This is not what is meant by 
commensalism. 


Quaint Associations 


A curious inter-relationship has arisen between slender 
fishes called Fierasfer and the sausage-like sea-cucumbers. 
When the fish touches a sea-cucumber it feels its way to 
the hind-end and then suddenly thrusts the tip of its tail 
into the food-canal. It then insinuates its whole body ina 
very deliberate way and disappears for a while into its 
strange shelter. For that is what the association seems 
tomean. The Fierasfer sometimes utilises a large bivalve, 
but it does not try to get into creatures in which there are 
not fresh currents of water. It is a light-avoiding fish, 
related to the sand-eel, but it cannot endure stagnancy. 
For such a case and for the little fishes that swim about 
under the umbrella of a large medusa the term shelter- 


205 


206 SCIENCE, OLD AND NEW 


association will perhaps suffice. This is not what is meant 
by commensalism. 

It is difficult, however, to draw a firm line where shelter 
stops and something more begins. There is a brilliant 
Indian Ocean fish, called Amphiprion, about two inches 
long, that lives in association with a large reef-anemone 
(Discosoma). So far as we know, it has not been found 
away from the sea-anemone, and if it is removed it soon 
dies. It lives among the tentacles and retires into the 
food-canal on the slightest alarm. As Mr. Banfield says in 
his delightful My Tropic Isle (1910), ‘‘it is almost as 
elusive as a sunbeam, and most difficult to catch, for if the 
anemone is disturbed it contracts its folds and shrinks 
away, offering an inviolable sanctuary.’’ The benefit to the 
fish is plain enough, it finds shelter and crumbs, but is 
there any benefit on the other side which would bring 
the case within the rubric of commensalism? Many sea- 
anemones are in the habit of stinging and seizing small 
fishes which intrude inquisitively or incautiously, but 
Discosoma does not seem to object to Amphiprion. It 
has been suggested that the brilliant colouring of the fish 
may serve as a lure, but it seems more probable that the 
movements of the fish in and about the sea-anemone help 
to keep up useful currents of water. 


Mutual Benefit Societies 


Commensalism at its best is a mutually beneficial, exter- 
nal partnership between two animals of different kinds. 
The typical case is the familiar association between a 
hermit-crab anda sea-anemone. The hermit-crab, having 
a very vulnerable tail—an unusually large Achilles’ heel, 
borrows the shell of some sea-snail, such as the whelk or 
buckie. In certain large kinds of hermit-crab it is the 
rule to put sea-anemones on the back of the borrowed 
shell. This is done in a very deliberate way, the hermit- 


COMMENSALISM 207 


crab coaxing the sea-anemone off its substratum, gripping 
it by the middle, turning it upside down, and then holding 
it in the proper position on the shell until it grips. When 
a hermit-crab has grown too large for its whelk-shell, it has 
to flit, leaving the partner sea-anemones behind. On such 
occasions it has been seen shifting the anemones from the 
old shell to the new. The sea-anemone masks the hermit- 
crab’s bad reputation (for there must be something 
corresponding to this) for voracity and pugnacity, and it 
has batteries of stinging-cells that may be useful at a crisis. 
The hermit-crab carries its partner or partners about, 
whereas ordinary sea-anemones are sedentary; and there 
are crumbs that float up to the sea-anemone’s tentacles 
from the crustacean’s often-laid table. The advantages 
are on both sides, and this 1s typical commensalism. 

There is much that is interesting in this well-known type 
of commensalism which would reward further experi- 
mentation. Thus there are cases where the sea-anemone 
is almost always found associated with the hermit-crab 
(e.g., the British Adamsia palliata on Eupagurus pri- 
deauxit), and there are cases where the sea-anemone plays 
an active part in re-establishing a lost partnership. 
Colonel Alcock has described a quaint case where the 
anemone settles down on the hinder part of the young 
hermit-crab’s tail, and the two creatures grow up together 
in a most intimate manner, the spreading sea-anemone 
forming a ‘‘blanket which the hermit-crab can either draw 
completely forward over its head or throw half back as it 
pleases.” This is striking enough, but what are we to 
say of cases like the shore-crab, Melia, where a sea-ane- 
mone is carried on each of the great claws or forceps and 
brandished about as if it were a weapon? ‘This is un- 
commonly like one animal making a tool of another. 
Our interest increases when we learn that if the crab is 
robbed of its partner it appears to be greatly agitated. 
“Tt hunts about on the sand in the endeavour to find it 


208 SCIENCE, OLD AND NEW 


again, and will even collect the pieces, if the anemone is 
cut up, and arrange them in its claw.” 


Experiments in Evolution 


When we take a broad view of the associations between 
different kinds of animals, we get the impression that a 
good deal of experimentation is tolerated as long as it is 
not disadvantageous, and that when some marked benefit 
accrues the association becomes fixed and elaborated. 
Thus various kinds of zoophytes may be found growing on 
the shells tenanted by hermit-crabs, and most of them are 
neither here nor there. But in certain cases the note of 
utility is struck and Nature’s sifting begins. We see this 
in the zoophyte colony Hydractinia, very interesting on 
account of the polymorphism or division of labour among 
its members, which often grows over a hermit-crab’s 
borrowed shell. The association is profitable to the 
zoophyte which is carried about and also gets crumbs 
from the hermit-crab’s meals. The association is profit- 
able to the hermit-crab, which is masked by the innocent 
zoophyte growth. But there is another advantage, that 
the zoophyte lightens the hermit-crab’s borrowed shell 
by absorption, and that it enlarges it at the mouth by an 
extra growth of its own, so that the crustacean can retain 
its house for a longer time—and the longer the better 
for the Hydractinia! 

Cases of commensalism and allied associations are very 
interesting in themselves and in the problems of animal 
behaviour which they raise, but they also disclose a wide- 
spread tendency throughout animate Nature—the tend- 
ency to link one organism with another in the Web of Life. 
They illustrate the integrative trend of organic evolution. 
If the struggle for existence is a formula for all the answers- 
back that living creatures give to environing difficulties 
and limitations, it includes not only competition but 


COMMENSALISM 209 


co-operative tactics as well. Struggle includes symbiosis. 
Just as there is correlation of organs in the body, so there is 
correlation of organisms in the economy of Nature. Not 
only have we to think of epizoic encrustations, of shelter 
associations, of masking, of external commensalism, of 
internal symbiosis, of parasitism and the like, but of the 
linkage between flowers and the pollinating insects that 
visit them, between fruits and the birds that distribute 
their seeds, between ants and aphids, between liver-fluke 
and water-snail, between rats and plague, between trout 
and orchards, between malaria and minnows, and so on 
endlessly. As Locke wisely said: ‘‘Things, however 
absolute and entire they seem in themselves, are but 
retainers to other parts of Nature.” 


The Value of Linkages 


The general suggestion that stands out is this: It looks 
as if there were in animate Nature a tendency to establish 
inter-relations, and that these inter-relations (if they are 
not on the parasitic tack) must make for progress. The 
way in which the progress is brought about is twofold, 
first, inasmuch as the working out of a linkage means an 
external registration of some step—a step worth taking if 
the linkage stimulates—and, second, inasmuch as the 
external system of inter-relations, always becoming more 
intricate, forms part of the sieve by which further new 
departures or variations are sifted. There has been an 
age-long evolution of sieves, which partly accounts for the 
progressive evolution of the sifted. 











































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Tarte . Ve i a he Me ae _ ae M Wh 





XXVIT 


SYMBIOSIS 





SYMBIOSIS 


THIs is a good term, worth retaining in a more or less 
strict usage, to denote a mutually beneficial internal 
partnership between two living creatures of different 
kinds. For mutually beneficial external partnerships, 
such as that between some hermit-crabs and sea-anemones 
there is the satisfactory word ‘‘commensalism,”’ literally 
“eating at the same table.” For an association with the 
benefit all on one side there is the term parasitism. It 
seems desirable to keep ‘‘symbiosis” for a mutually 
beneficial internal association, and there is in the word 
(‘living together’) a suggestion that the linkage is in- 
timate, affecting the metabolism of both partners. 


Lichens as Dual Plants 


It was the botanist De Bary who first applied the term 
symbiosis to the partnership illustrated by lichens. For 
he was one of those who established the interesting fact 
that these encrusting plants, so familiar on rocks and 
trees, are dual organisms. They represent a firm, consist- 
ing of fungoid partners, which fix and absorb and protect, 
and of alga partners, which have chlorophyll or some allied 
pigment and are able to build up carbon compounds. The 
fungus partners, which supply the water and salts, some- 
times get the upper hand and absorb their partner alge, 
without which, however, they cannot continue to live. 

arg 


214 SCIENCE, OLD AND NEW 


The alga partners sometimes manage to get along in 
water without their associated fungus, but they flourish 
best in symbiosis. It is interesting that the fungus part- 
ners, which normally absorb water and dissolved salts, 
sometimes take to absorbing decayed organic matter 
(sinking to the saprophytic diet which many fungi illus- 
trate), and may go further and take to absorbing food 
from the living tissues of a tree (sinking to the parasitic 
mode of life, which is also very common in the class). 
Lichens thus show how certain fungi have found a new 
modus vivendt by entering into co-operation with certain 
alge; but from this partnership, as we have seen, there are 
occasional relapses. 


The Secret of the Heather 


Everyone recognises that heather grows well on poor 
and unpromising soii where relatively few other plants 
will thrive, but what is the heather’s secret? It has a 
partner fungus which sends its threads not only into the 
cells of the root but into stem and leaves and even into 
the seed-box. The fungus acts as the intermediary be- 
tween the heather and the soil; it absorbs water and or- 
ganic material; it is perhaps able in some measure to fix 
atmospheric nitrogen. Jn any case, the heather has been 
able to effect a compromise with what was probably to 
start with a predatory intruder; indeed, the compromise 
has gone so far that the heather cannot thrive without its 
partner. This, again, is symbiosis, and it is now known 
to occur in a large number of plants. In many cases, such 
as beech and pine, the partner fungus or mycorhiza 
confines itself to the outside of the root, forming a dense, 
absorbing felt-work, which though not indispensable to the 
life of the tree is certainly valuable. The fungus absorbs 
water and salts and organic materials from the soil and 
passes these on to the tree; the benefit it gets in return is a 


SYMBIOSIS 215 


supply of carbohydrates from the root. As the threads 
of the fungus do not usually penetrate into the root-cells 
the partnership is external in this case, while it was internal 
in the case of the heather, which shows the impossibility 
of hard and fast definition, for the physiological condition 
is the same in both, and both must be included as forms 
of symbiosis. 

The linkage becomes subtler in some of the orchids, 
like the bird’s-nest orchis of our woods, for while there are 
cells in the host-plant which live in partnership with the 
spreading fungoid filaments, there are others of a very 
peculiar type which attack and digest these. In this way, 
as Professor Bower puts it, ‘“‘the intrusive fungus is kept 
within bounds, and headed off from tissues of vital im- 
portance’’; and the digestion is in itself profitable, for the 
fungus has worked up valuable nutritive materials in its 
threads. It is a curious case this—of eating the cake and 
yet having it, and the orchid’s digestive cells are strangely 
suggestive of the amoeboid phagocytes which ingulf and 
digest intruding bacteria and perform other useful offices 
in our body. 


Root Tubercles 


An interesting form of symbiosis is seen in the root- 
tubercles which occur on almost all leguminous plants and 
in some other cases. It seems that motile bacteria pass 
from the soil into a root-hair and spread in a thread-like 
trail from cell to cell. In the rind of the root, where a 
rootlet would arise, the bacteria provoke the bean or the 
clover, or whatever it is, to form a gall-like tubercle, and 
in this they multiply apace, becoming curiously branched 
and turgid ‘‘bacterioids.”’ Jn some way or other, in the 
presence of the sugar and proteins of the root, they are 
able to fix free nitrogen from the air, and this goes to the 
enrichment of the host-plant, which is continually digest- 


216 SCIENCE, OLD AND NEW 


ing its partners by a sort of vegetable phagocytosis. The 
partnership is so thoroughly established that the legumi- 
nous plants cannot thrive without their bacteria; it looks 
like another case of making a friend of a foe. The fixation 
of free nitrogen means a great improvement of the soil, 
and it is certainly an admirable performance however it is 
brought about. What man does by means of dynamos 
which send high-tension arcs through the air, the sym- 
biotic bacteria do very quietly in the roots of the beanstalk. 


Plants in Partnership with Animals 


Among animals also symbiosis is common. Almost all 
the minute Radiolarians, with exquisitely beautiful skele- 
tons of flint or of acanthin, have partner alge in their 
transparent living matter. They float on the surface of 
the open sea, often in countless numbers, and the variety 
of their kinds is legion—over 5,000 species having been 
described. Perhaps their success is partly due to their 
symbiosis. In the sunlight, the partner alge can utilise 
the carbon dioxide which the animal protoplasm produces, 
liberating oxygen which must be useful to their bearer. 
The alge are capable of photo-synthesis and the carbon 
compounds they build up can be utilised by the Radio- 
larian. The two kinds of creatures work together as if they 
formed afirm. ‘The symbiosis is a mutual benefit society. 

The same kind of co-operation is illustrated by a number 
of green Protozoa, in cases where the green colour has 
been shown to be due not to the animal having learned 
the plant’s secret of manufacturing chlorophyll, but to a 
partnership with minute alge (Zoochlorelle and Zooxan- 
thellz). There are probably a few green Protozoa, like 
Euglenids and a green bell-animalcule, which have chloro- 
phyll of their own, but most green animals are instances of 
symbiosis. This is true, for instance, of the green species 
of Ameeba, the green fresh-water sponge, the green Hydra, 


SYMBIOSIS 217 


some green sea-anemones, many livid green corals, and 
the well-known Planarian worm called Convoluta. In all 
these cases the partner algz utilise the carbon dioxide and 
nitrogenous waste produced by the host-animal, which in 
turn gets oxygen and carbon compounds from its symbions. 
And it is always open to the dominant partner of the firm 
to digest his partners. There can be no doubt that this 
kind of symbiosis is profitable, for it is widespread, and its 
occurrence enables us to understand better the emptiness 
of the food-canals in many flourishing coral-colonies. Ata 
lower level there is a case on record of a colony of thousands 
of green Amcoebe which lived for ten years in a glass vessel 
without a particle of solid food, the animal depending 
entirely on what its symbions produced. 


Grades of Symbiosis 


There is naturally considerable variety in the intensity 
of the symbiosis. It may be a casual or a constant part- 
nership; it may be an advantage to life or absolutely 
indispensable. In the green Convoluta the egg is without 
any associated alge, but the young larve must be infected 
if the development is to continue; the interdependence is 
very intimate. In the green Hydra the egg is infected 
before it is separated from the parent, but the symbions 
are not in this case indispensable. Many years ago Whit- 
ney made the neat experiment of keeping a green Hydra 
for a fortnight in a 5 per cent. glycerine solution at 20° 
centigrade, with the result that the minute green alge, 
which live inside the inner layer or endoderm cells all died. 
The Hydra thus became wan white and so it remained 
for over two months without a trace of green. It fed in 
the usual Hydra fashion on small animals, and it budded 
in the normal way. In this case, therefore, the symbiosis 
is evidently not obligatory, though it is doubtless ad- 
vantageous. 


218 SCIENCE, OLD AND NEW 


It is difficult to draw a firm line between symbiosis and 
parasitism, especially when we understand that there is a 
tendency to work out a live-and-let-live compromise 
between parasite and host. An intruding parasite, like 
the fungus in the heather, may be tamed into a symbion. 
On the other hand, a symbion may perhaps sink into a 
parasite. In the food-canal of animals there is often an 
occurrence of useful bacteria and infusorians which facili- 
tate the digestive processes, and although these are not 
inside the tissues it would be pedantic to exclude them 
from the ranks of symbions. Similarly, yeast-cells of 
various kinds are often found in the food-canal of insects 
and seem to be of value in operating upon and improving 
the food-material. When the pomace-fly, Drosophila, is 
feeding on fermenting fruit, it must have yeasts to help it, 
and this kind of partnership is of wide occurrence. 

A quaint heresy has been started more than once in the 
last few years that all living creatures except bacteria 
illustrate symbiosis, the idea being that certain formed 
bodies in the microcosm of the cell are tamed bacteria 
which have come to be indissolubly bound up in the bundle 
of life with their bearers. There is no good case to be 
made for the heresy, but it is interesting as an exaggeration 
of the truth that there is a widespread tendency in the 
realm of organisms to link lives together, to establish 
inter-relations. 


XXVIII 
ODDITIES OF DIET 





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ODDITIES OF DIET 


In the matter of food we often show absurd prejudices. 
We smile at the Chinese who make a rather costly soup 
out of the nests of the Sea-Swift (Collocalia), but as the 
whitish nests are made of consolidated salivary juice from 
the bird’s mouth the soup is probably very digestible. 
As to taste, that is a matter of opinion. The Japanese 
eat dried jellyfishes, but what could make a more delicate 
sandwich? And as to sea-cucumbers, the béche-de-mer 
so much appreciated in the East, they are certainly as 
inviting as the sausages which they resemble. Once a 
year the waters around Samoa are thick with the wriggling 
headless bodies of Palolo-worms that have swarmed out 
of the coral-reefs. The sea is like vermicelli soup, and the 
natives catch the worms in basketfuls and have a great 
feast. But this is just as reasonable as enjoying caviare, 
which consists of the roe or eggs of the sturgeon. We 
shrug our shoulders at people who eat big grubs or locusts, 
or who nibble at the raw arm of a cuttlefish as we eat celery, 
but it is mainly prejudice. And we must also remember 
what a treat anything fleshy must be to people who are 
forced to live all the year round on mealy food. It is sheer 
prejudice to despise the toothsome periwinkle—‘‘the 
poor man’s oyster,’”’ as it has been called; and it is absurd 
to turn up our nose at the palatable snail and the delicate 
muscle of the frog. But we wish to think of oddities of 
diet in animals, not in men. 


221 


222 SCIENCE, OLD AND NEW 


Peculiar Feeding Habits 


In South Africa those who know where to hide some- 
times see the Aard-Vark, an antediluvian animal, belong- 
ing to the sloth-anteater order of Edentates. It rests well 
concealed during the day and comes out at dusk to hunt 
for food. It has a long, somewhat piggish, snout and a 
worm-like tongue, which is whipped out and in with great 
rapidity. The Aard-Vark is particularly fond of burgling 
the earthen fortresses of the termites or white ants. When 
it has made a hole in the wall it sticks in its snout and its 
sticky tongue works like lightning, out and in, out and 
in, until the big creature has had enough. It is a strange 
way of feeding. The Common Cuckoo is particularly fond 
of kairy caterpillars, which most insectivorous birds leave 
severely alone, for the hairs are often very irritating. But 
here is one of the many ways in which the cuckoo breaks 
through bird rules. It eats so many woolly caterpillars 
that the hairs form a thick feltwork inside its stomach. 
There is a touch of the unique about this. 

If you stir up a big ant hill in the woods—once in a 
season will be enough—you detect a strong odour. That 
is formic acid (Formica, an ant), and all ants, whether 
they sting or not, secrete formic acid—corrosive and un- 
palatable. Because of this the majority of birds leave ants 
alone, except as an occasional mustard to their food, but 
there are some woodpeckers that delight in them. Overa 
thousand ants have been taken from the crop of a wood- 
pecker, which means a considerable quantity of formic 
acid. Again, we get the impression that some animals 
seek out oddities of diet. There is often an unexpected- 
ness about the food! 


Clothes-Moths 


Many people are familiar with clothes-moths, minute 
greyish creatures that sometimes fly out when we disturb 


ODDITIES OF DIET 223 


clothes that have been left hanging for a long time. But 
very few people have thought about these insects, for 
calling them bad names is not thinking. They do great 
damage to clothes and furs, and they are very exasperat- 
ing in their destructiveness. It is easier to keep them out 
than to get them out when they have got in. One way 
is to use something like naphthalene-balls, for the moths are 
repelled by the strong odour; and the trouble begins when 
the female moth lays its eggs in the muff or woollen stuff. 
Another way is to wrap the fur up in tissue paper, for the 
moth cannot break through. We have known of precious 
skins remaining untouched for many years simply because 
there was no hole in the tissue-paper wrappings. 

Out of the eggs come very minute and very slender 
larvee, and they devour the hairs of the fur or of the woollen 
fabric, and it is an interesting point that they will not 
touch vegetable hairs or fibres. Thus they have no use for 
cotton-wool or paper. The larva feeds and grows and 
moults, and when colder weather comes it spins some hairs 
together into a tiny tube, and lies quiet, undergoing a slow 
change into a moth. There is nothing very remarkable 
in all this—except in the sense that everything is remark- 
able—but what makes us rub our eyes is the food. For 
what is hair made of but horn (or keratin), and no more 
indigestible stuff could be imagined. A man may swallow 
a dozen shrimps ‘‘holus bolus,’”’ but, so far as we know, 
he makes nothing whatever of the husks of chitin. They 
are almost quite indigestible, and the same must be said 
of horn. The answer to the puzzle is probably that the 
larva of the clothes-moth has partner micro-organisms 
(yeasts) in its food-canal which enable it to deal with the 
horny hair. 

If we understand the case of the clothes-moth, we 
cannot be surprised that there are special larve that feed 
on the horns and hoofs of dead animals. There is also a 
whole order of somewhat lice-like insects (Mallophaga) 


224 SCIENCE, OLD AND NEW 


which live as parasites on the feathers of birds and hairs 
of mammals, especially while these are still young. As 
long as the feathers and hairs are growing the insects will 
get some living matter to eke out the horn, and it must be 
admitted that some of the insects in question suck blood 
like true lice. 


Wax-Moths 


Another strange case, well known to bee-keepers, is that 
of the larvee of the Wax-Moth. They make silk-lined 
tunnels through the comb and do much damage. What 
particularly interests us at present is that these larve 
eat wax—a non-nitrogenous carbon compound that no 
other creature can make any use of. It seems that the 
larvee of the Wax-Moths must have wax to eat, but as no 
animal can live without nitrogenous supplies this cannot 
be their sole food. They pick up unconsidered trifles in 
the form of pollen grains and the dead bodies of bee-grubs; 
and so they manage to eke out a meagre subsistence. 


Sea-Cucumbers and Earthworms 


As in the last case, some ways of feeding are’ not so 
strange as they appear at first sight. A sea-cucumber is a 
sausage-shaped animal with a wreath of branched ten- 
tacles around the mouth. In many cases the sea-cucum- 
ber feeds in a quaint way. It immerses one of its tentacles 
in the adjacent mud and then plunges it into its mouth, 
as a boy might deal with his treacle-covered fingers. 
Then the sea-cucumber does the same with another 
tentacle, and so on all round. But the creature is not 
eating mud; it is utilising the minute organisms and or- 
ganic particles which the mud contains. And so, of course, 
with the earthworms, which eat their way through the 
soil. That in itself is of no use for food, but it contains 


ODDITIES OF DIET 225 


rotting fragments of plants which the earthworms digest, 
while the finely ground soil is passed out in the form of 
““castings,’’ so familiar on lawns and putting-greens. The 
same is true of many seashore animals that eat sand, such 
as the Fisherman’s Lobworm; it is not the sand that 
counts, but the multitude of minute creatures or, it may 
be, ‘‘crumbs’’ which the sand includes. 


Necessity and Invention 


What does it all mean—this feeding on termites, hairy 
caterpillars, ants, hair, horn, wax, mud, and so forth? 
We may be sure that it is not caprice. It is an indication 
of the stringency of the struggle for existence, and of the 
tendency that all hard-pressed living creatures have to 
take advantage of any vacant niche of opportunity. If 
there is a corner that other competitors are not occupying, 
it will soon be possessed. If there is a kind of food that 
other competitors are disdaining, it will soon be appre- 
ciated. It is by specialising in habitats and diets that 
so many different kinds of creatures can get on together 
in the same surroundings. So these oddities of diet are 
not what might be called ‘‘curiosities,’”’ they have a deep 
significance. They illustrate the biological insight of the 
old tag: ‘‘Jack Sprat could eat no fat; his wife could eat 
no lean.” That was how they managed to get on at all; 
and it is the same in Wild Nature. This sheds a new light 
on the old saying: Nature abhors a vacuum. The river 
of life is always in flood, filling every vacant corner. The 
great majority of animals die young; can we wonder that 
all sorts of food-materials are tried? Necessity is the 
mother of invention, and perhaps we should not forget 
the father—Curiosity. 

The last remark applies particularly to cases among the 
higher animals, where a change of diet is in progress, or 
where some novel item is included in the menu. Thus 


226 SCIENCE, OLD AND NEW 


there seems no doubt that during the present century the 
Herring Gull in Scotland has become more vegetarian 
than it used to be. Jt is naturally a fish-eater; but it is 
taking more and more to the harvest fields, and it has 
become very expert in gouging out turnips. In the same 
way the New Zealand Parrot or Kea, naturally a fruita- 
rian, has learned, in a comparatively short time, to kill 
sheep for the sake of the fat about the kidneys. In the 
same way an individual cat may become very fond of 
green meat, including cabbages. Perhaps the last case is 
pathological, but all these idiosyncrasies have their in- 
terest. They illustrate variations in habit, and some of 
them may be among the raw materials of future evolution. 
But to expect the lion to make a habit of eating grass like 
the lamb seems to the zoologist somewhat optimistic. 


XXIX 


PLANTS LIVING IN INSECTS 






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PLANTS LIVING IN INSECTS 


EVERY year brings increased knowledge of the Web of 
Life, and one of the recent revelations has been the extent 
to which plants live inside insects in an intimate partner- 
ship or symbiosis. Just as a lichen on the wall is a double 
plant—an Alga and a Fungus living together with profit 
to both, so many an insect is a mutual benefit society! 


Bacteria of Cockroach 


In the common cockroach and in all its relatives that 
have been examined there are bacteria living inside the 
cells of the reserve tissue known as the fatty body. These 
bacteria are not harmful but friendly, and they pass on 
from one generation to another. They enter the egg 
before it leaves the mother-insect; they multiply within 
the embryo; they sojourn for a short time in the develop- 
ing food-canal, and then they find their headquarters in 
the fatty body. In one of the common wood-eating ants 
there is a similar partnership. The cells lining the diges- 
tive part of the food-canal always contain the threads 
of a slime-fungus, sometimes like an extremely minute 
ball of twine; and in this case also there is very early 
infection of the egg cell and a multiplication within the 
embryo. It must be noted that we have to do not with a 
general distribution of the fungus throughout the insect, 
but with a localised occurrence in the wall of the food- 
canal. 

229 


230 SCIENCE, OLD AND NEW 
Yeasts of Death-Watch 


Most of us are familiar with ‘‘death-watches” which 
make tapping noises in the wainscot. The sounds are 
made by the male thumping his head against the wood as 
a signal to his desired mate; so they speak of love, not of 
death! These death-watches remain young for a long 
time and the larve bore in wood and other dry materials, 
including books. One kind is the ‘‘biscuit weevil,’’ too 
well known to sailors, and it is a quite extraordinary 
illustration of the kind of symbiosis or living together that 
we are describing. At the beginning of the digestive part 
of the food-canal—we envy the man who can dissect a 
biscuit weevil—there are two minute pouches, and these 
are crammed with yeast-plants. The insect has an inter- 
nal brewery; but whether the yeasts ferment the wood, or 
whether they capture nitrogen in some way, is uncertain. 

Microscopic examination showed Professor Buchner that 
there were no yeast-plants in the eggs, yet the young 
grubs always have them. The solution of this puzzle is 
almost incredible. Associated with the egg-laying appara- 
tus in the female beetle there are two minute reservoirs 
opening to the exterior, and these are full of yeast-plants. 
When an egg is laid some yeast-plants are expelled, and 
they adhere to the shell, which is rough all over. When the 
beetle-grub that develops from the egg is ready to hatch 
out, it nibbles at the shell, and thus its food-canal is 
stocked with yeast-plants. Only a few need be swallowed, 
for yeast multiplies with great rapidity. A little leaven 
goes a long way with these death-watches. The whole 
story is almost eerie. It is one of the very few cases in 
which the partner-plant is not handed on inside the egg. 


Utilising Unpromising Food 


One of the dangers of unskilled vegetarianism is having 
to eat too much cellulose, for man does not seem to have any 


PLANTS LIVING IN INSECTS 231 


digestive ferment for dealing with that material, which 
forms the cell-walls in all ordinary plants. What happens 
is that bacteria in the food-canal attack the cellulose, say 
in the lettuce, the cabbage, the celery we eat, and change 
it into sugars. So the unskilled vegetarian is apt to ask 
too much of his bacteria, which, moreover, are apt to 
carry their work of fermentation far beyond the limits of 
utility. We are not forgetting that sheep and cattle live 
very largely on grass, and yet they are also without cellu- 
lose-digesting ferments. But they have got various 
contrivances which man has not got, such as the paunch 
which contains a huge army of bacteria. This apparent 
digression was necessary in order to enable us to understand 
those caterpillars that live on most indigestible materials. 
We have already taken the case of clothes-moths. Wedo 
not suppose that the adults require much if anything to eat, 
but the tiny caterpillars require a great deal, for they have 
to grow. Yet what do they feed on but hair, which is 
made of keratin or horn. It is difficult to think of any- 
thing more indigestible, and yet it is digested. They say 
that sheep can grow fat on blotting-paper; the larve of 
the clothes-moth thrive on wool. In both cases the re- 
quired fermentation is brought about by bacteria in the 
food-canal. It will be noted that in these instances the 
partners live freely in the cavity of the food-canal, whereas 
in the cockroach and the death-watch they live inside 
certain cells. 


Bacteria of Green-Flies 


As long ago as 1858 Huxley described in green-flies or 
aphids a peculiar paired organ which he called a ‘‘pseudo- 
vitellus,’”’ because its contents looked yolk-like. But it 
was not till about ten years ago that the nature of this 
enigmatical organ was discovered. It consists of strands 
of cells which are packed with bacteria, bearing a very 


232 SCIENCE, OLD AND NEW 


close resemblance to the nitrogen-capturing bacteria that 
form tubercles on the roots of leguminous plants like peas 
and clovers. The organ is a sort of culture-ground for 
partner bacteria which probably capture nitrogen for the 
green-fly. In any case they are friendly, not hostile. 
These aphids are viviparous all through the summer 
months, and the fully-formed young creatures that leave 
the mother have already their stock of bacteria. ‘The 
useful infection takes place in the early embryo. In 
autumn, however, the aphids are oviparous, and in this 
case the infection takes place through a minute aperture 
in the envelope of the egg. Besides aphids there are 
some other sap-sucking insects with partner plants, such 
as scale-insects and cochineal-insects and frog-hoppers; 
and Buchner has described several Cicadas in which there 
are actually two kinds of symbions always present in the 
same insects, sometimes independently and sometimes in 
very close combination. Wheels within wheels again! 


The Gnat’s Bite 


The gullet of the common gnat bears three minute 
pouches, and these contain gas-producing fungi which in 
certain circumstances become very numerous. ‘Thus if 
the gnat is fed on fruit-juice, they multiply greatly and 
they may kill the insect with their gas-production. Ac- 
cording to Schaudinn and others, some of these fungi 
get into man’s skin when the gnat or mosquito inserts its 
stilets. It may be that the gas, probably carbonic acid 
gas, hinders the coagulation of the victim’s blood, while a 
ferment also produced by the fungi increases the blood- 
pressure and irritates the skin. The typical irritation can 
be produced apart from any bite, by rubbing the gullet 
sacks on man’s scratched skin! 

In the seventeenth century two of the pioneer micro- 
scopists, Hooke and Swammerdam, described in the louse 


PLANTS LIVING IN INSECTS 233 


a peculiar little organ, the ‘‘stomach-disc.”’ Two or three 
years ago the meaning of the organ was discovered by 
Sikora and Buchner. It is one of these incubation- 
organs; it is a mass of intracellular rod-like fungi. There 
are special arrangements for infecting the ova, so that 
every louse has its partners from birth. The probability 
is that the fungi produce a ferment which passes into the 
skin of the victim and causes local increase of blood- 
pressure, thus facilitating suction. The partnership has 
been demonstrated in several kinds of lice, and the bed- 
bug shows it too. 

We have taken these examples from Professor Buchner’s 
remarkable book, Tuer und Pflanze in intrazellularer 
Symbiose (1921), where scores of others may be found. 
It will be seen that the linkage occurs in many different 
kinds of insects; that except in two cases it is established 
in the egg to begin with by ante-natal infection; that it 
finds realisation in various parts of the insect’s body; that 
it is turned to various uses; and that the symbions are of 
different kinds—bacteria, yeast-plants, slime-fungi, and 
other fungi. We wonder how the varied partnerships 
arose, whether the insects have been able to domesticate 
and tame what were originally intruders. We wonder also 
to what extent the partner-plants have changed the ways 
of the insects. 





XXX 


THE CAT AND THE MOUSE 


235 





THE CAT AND THE MOUSE 


MANY common sights are very puzzling, as the wise 
man said long ago in regard to the way of the vulture in the 
air, the way of the snake on the rock, and some other 
things. One of these puzzling sights is the way of a cat 
with a mouse. In many cases, as everyone knows, it 
does not kill its victim outright, but allows it to escape 
and catches it again. Many times over it repeats the 
performance. What is the interpretation? 


Theories of the Cat’s Behaviour 


Some people see in the cat’s behaviour a flagrant in- 
stance of what they call ‘‘the cruelty of nature.’’ In most 
cases the violent death that one animal meets at the hands 
of another is almost instantaneous; we once timed a 
golden eagle killing another bird, and the episode was over 
in less than thirty seconds. It seems rather hypocritical 
as well as anthropomorphic to call this cruel. But the 
case of the cat and the mouse is different. The cat pro- 
longs the process; it looks as if it teased its dazed victim; 
and Romanes, who was one of the pioneers of comparative 
psychology, committed himself to the view that the cat 
shows a delight in torture. But this is too sophisticated 
for a cat; it needs a man to have so barbarous a gratifica- 
tion. Others have suggested that the cat does it to whet 
its hunger, and they interpret the fact that the cat often 
leaves the mouse uneaten as due to a failure of the psy- 


237 


238 SCIENCE, OLD AND NEW 


chical appetissant. Here it may be noted that cats are 
keen sportsmen, and will kill creatures which they never 
eat. Thus a cat will kill a shrew, but the odoriferous 
gland along the side of the shrew seems to be repellent, 
and we never heard of a shrew being eaten by a cat. But 
no one could expect an instinctive impulse to discriminate 
in any hard and fast way between catching a mouse and 
catching a shrew. 


A Form of Play 


Another suggestion is that the cat teases the mouse to 
improve its flavour, but this, again, is grotesquely an- 
thropomorphic. It is reading the man into the beast. 
The true interpretation, which does not strain our credu- 
lity, is this—that the cat is playing. There are many 
animals which play when they are young, and it is hardly 
too much to suggest that their youth is prolonged so that 
they may play. For the biological interpretation of play 
is that it affords an apprenticeship to the business of life 
before responsibilities become serious, that it is a time 
when instinctive behaviour is often modified by intelligent 
learning, and that it gives elbow-room for testing idiosyn- 
crasies and new departures. As Groos has so well shown, 
play is not a trivial thing, but essential; it is a vital part of 
animal education. The play of lambs, kids, puppies, 
kittens, and many other mammals is familiar, and one of 
the forms of play is the sham-hunt. Everyone knows how 
the kitten chases the ball of worsted or the wind-blown 
leaf, catches it, lets it go, catches it again. The moving 
object pulls the trigger of the hunting impulse, and even 
when the kitten is very tired it cannot resist one more 
hunt when you roll the ball past its nose. 

Brehm prettily describes the familiar sight. ‘‘The 
playfulness of kittens is marked when they are very young, 
and the mother does everything to encourage it. She 


THE CAT AND THE MOUSE 239 


becomes a child with her children from love of them, just 
as a human mother forgets her cares in play with her little 
ones. The cat sits surrounded by her family and slowly 
moves her tail, the indicator of her moods. The kittens 
hardly grasp its language as yet, but they are excited by 
the motion, their eyes take on expression and they prick 
up their ears.’ The play has begun, and it is interesting 
to watch it becoming more complex, for by and by the 
kitten will lie in wait for the moving ball of worsted and 
will spring upon it like a tiger. 

But not only does the mother-cat share in her kitten’s 
play, she may occasionally relapse into a game when she 
is by herself; and this is the interpretation of the cat’s 
way with a mouse—she has returned to her juvenile 
playfulness. This persistence of play into adult years is 
seen in some other mammals; it is beautifully illustrated 
by otters, and we have seen even the sedate sheep for- 
getting themselves! 


The Mousing Instinct 


Some experiments made a good many years ago by Mr. 
C. S. Berry tended to show that cats learned by imitation 
to kill mice. An unprejudiced uninitiated cat would allow 
a mouse to perch upon its back. The cat’s interest was 
not aroused till the mouse ran. But subsequent experi- 
ments by R. M. Yerkes and D. Bloomfield showed con- 
clusively that young kittens react to mice in a way that 
differs radically from their reaction to a moving ball. The 
killing instinct appears suddenly, usually during the 
second month. In a moment the playful kitten is trans- 
formed into a beast of prey. It bristles up its hair; it 
switches its tail; it may hiss, spit, or growl; it unsheathes 
and sheathes its claws; it catches the mouse by the back 
of the neck. The movement of the mouse seems suddenly 
to liberate an inborn capacity, a ready-made trick, an 


240 SCIENCE, OLD AND NEW 


instinct; but the odour of the mouse counts and counts 
increasingly. If the kitten grows up unexperienced, the 
instinct seems to become more and more difficult to evoke; 
but the young kitten can kill in the fit and proper way 
without either experience or imitation. At first the killing 
tends to be immediate; ‘‘playing with the mouse’’ comes 
later. 

““Instinct”’ is one of the most abused of words. People 
speak of the political ‘‘instinct,”’ the ‘“‘herd-instinct,’’ the 
‘“‘sex-instinct,’’ the predatory ‘“‘instinct,’”’ the religious 
““instinct,’’ the feminine ‘‘instinct,’’ the physician’s ‘‘in- 
stinct,’’ and so on till one is tired. Yet the zoologists 
have come to general agreement as to the meaning of 
“instinctive behaviour’’—the adjective is safer than the 
noun; and this meaning is well illustrated by what has 
been said of kittens killing mice. Instinctive behaviour is 
the expression of hereditarily pre-established linkages 
between certain nerve-cells and certain muscle-cells. 
When the button is pressed the performance comes off, 
one act giving the cue, so to speak, to the next act. The 
nerve-cells concerned are (1) the receptors (or scout-cells), 
(2) the adjustors (or G. H. Q. cells), which receive the 
tidings and pass them on, and (3) the motor or efferent 
nerve-cells (say executive-officer cells), which see that 
the muscles (the so-called ‘‘common soldiers”) obey 
orders. Instinctive actions do not require to be learned, 
though they may be perfected by practice. Unlike in- 
telligent actions, they do not require much attention from 
the G. H. Q. or adjustor cells; yet it often happens in 
birds and mammals, and occasionally in ants and bees, 
that G. H. Q. intelligence or ‘“‘perceptual inference’’ inter- 
venes at a critical moment. We do not believe that 
instinctive behaviour is without its psychical side; it has 
its cognitive and conative aspects in the inner life. To 
say the same thing over again, it is suffused with aware- 
ness and backed by endeavour. 


”? 


XXXI 


THE DANCING MOUSE 


241 





THE DANCING MOUSE 


ALTHOUGH the origin of this fascinating little animal is 
uncertain, the probability is that it arose in China some 
centuries ago as a freak or mutation from the common 
mouse stock. It is distinguished especially by its habit 
of waltzing round in circles of varying radius and of whirl- 
ing round with great rapidity. Perhaps in the strict sense 
it does not dance, but it is difficult to define nowadays 
what the term dancing includes. It is an interesting fact 
that variations like incipient dancing occasionally crop 
up among ordinary mice. In all likelihood the danc- 
ing mouse would have gone to the wall in wild nature, 
for it is a freak inclining to the pathological, but it came 
under the zgis of Japanese breeders, who took care of it 
and subjected it to artificial selection. It is now a well- 
established artificial race which breeds true. Its protec- 
tion is due to its whimsical ways, but whereas those 
brought to America and Europe are generally allowed to 
disport themselves in spacious cages where they have 
plenty of room for displaying their ‘‘circus-movements, ”’ 
those in the Far East are kept for the most part in confined 
boxes where they put mechanical devices into action by 
running round inside a drum-like wheel. 


Movements 


The scientific interest of the dancing mouse has been 
explained by Professor R. M. Yerkes in a monograph 


243 


244 SCIENCE, OLD AND NEW 


published in 1907 and in a number of subsequent papers, 
and what we have to say is dependent on these masterly 
investigations, for our personal experience of the charming 
creature is not worth talking about. 

Let us begin with the dance movements. Before the 
young mouse is able to leave the nest it begins to move in 
circles and to raise its head in a quick jerky way. At the 
age of three weeks it dances vigorously. It is extremely 
restless, “‘incessantly active when not washing itself, 
eating, or sleeping’’; it is continually lifting its head and 
sniffing with the nose pointed upwards; it whirls round like 
a top with all the feet close together underneath the body, 
or it runs rapidly round in circles of two to twelve inches 
in diameter with the feet spread widely, or it moves in 
figure-eight and zigzag fashion. Two mice often dance 
together, sometimes moving in the same direction, or one 
clockwise and the other anti-clockwise. There are left, 
right, and mixed whirlers, the first in the majority. They 
usually rest for most of the day, emerging towards dusk, 
and dancing with varying intensity for some hours. Zoth 
counted seventy-nine whirls without an instant’s interrup- 
tion, and Yerkes counted as many as one hundred and 
ten whirls. This indicates great power of endurance, 
specialised in a particular direction. 


Peculiarities 


We wonder that the whirlers are not overtaken with 
extreme dizziness, but this is one of the peculiarities. Ifa 
normal common mouse is rotated in a rapidly moving 
cyclostat it falls into convulsions, but the dancing mouse 
does not seem to mind much, if at all. It is exempt from 
the dizziness usually produced by rapid rotation, and also 
from visual dizziness when placed on an elevated surface. 
On the other hand, the dancing mouse shows more or less 
deficiency in the power of balancing (equilibration) and of 


THE DANCING MOUSE 245 


placing its body in a particular position (orientation). 
Furthermore, it is partially or totally deaf. 

These peculiarities led investigators long ago (1899) to 
inquire into the structure of the ear in the dancing mouse, 
and several of them discovered anatomical anomalies 
which they sought to associate with the animal’s unusual 
behaviour. Thus it was confidently stated that of the 
three semicircular canals around the ear, which have to do 
with balancing in ourselves, only one attained develop- 
ment in the dancing mouse. Another anomaly in the 
cochlea of the ear was described as accounting for 
the deafness. Unfortunately, however, the structure of 
the ear is an exceedingly difficult subject, and subsequent 
investigators have not confirmed what their predecessors 
believed they had discovered. There must be some struc- 
tural basis for the peculiarities of behaviour—the bizarre 
movements, the defective balancing power, the nervous 
jerking of the head, the insensitiveness to sounds. But 
it is not at present, we understand, possible to state what 
the correlated peculiarities of structure are, either in the 
semicircular canals, or in the cochlea, or in other parts of 
the ear, or in the brain, or in the rest of the nervous sys- 
tem. This is a very disappointing conclusion. 

Many animals have been labelled deaf because they did 
not respond in any way to certain loud noises. But the 
possible fallacy here is that the animal may fail to respond, 
not because it does not hear, but because it is not 
interested. Therefore Professor Yerkes tried the adult 
dancers with a great variety of sounds—clapping the 
hands, whistling, shouting, ringing a bell, causing another 
mouse to squeak, sounds to which ordinary mice respond. 
Working for three years with more than a hundred in- 
dividuals, he never got any reaction that could be referred 
with any fair degree of certainty to an auditory stimulus. 
The adult is totally deaf. But, curiously enough, Pro- 
fessor Yerkes’s work also showed that the young dancer 


246 SCIENCE, OLD AND NEW 


sometimes hears sounds for a few days during the third 
week of its life. One’s curiosity is heightened by the fact 
that shortly before the brief period of auditory sensitive- 
ness the young dancer becomes extremely excitable and 
pugnacious. 


Experiments 


By ingenious experiments, which rewarded the animals 
when they chose correctly and punished them mildly 
when they failed, Professor Yerkes was able to prove that 
the dancing mice can discriminate between different 
degrees of brightness, whether the light was reflected from 
cardboards of different kinds or was transmitted through 
ground glass. One mouse that he worked with for several 
weeks gradually improved in discriminating power until 
she was able to distinguish between two boxes whose 
difference in illumination was less than one-tenth that of 
the brighter box. “‘At the beginning of the experiments a 
difference of one-half did not enable her to choose as 
certainly as did a difference of one-tenth after she had 
chosen several hundred times. Evidently we are prone 
to underestimate the educability of our animal subjects.” 
Patient experiments, a model of scientific caution and 
precision, led Professor Yerkes to the conclusion that true 
colour-vision, if it exists at all, is extremely poor in the 
dancing mouse; and it is interesting to be able to associate 
with this the fact that while the retina has the usual rod- 
like cells of the typical mammalian retina, it has nothing 
closely similar to the cones, which are believed to have to 
do with colour-vision. 


Educability 


The dancer is quick and neat in its restless movements, 
but careful watching shows that two sometimes collide, 


THE DANCING MOUSE 247 


and that only those doors with which the animal is familiar 
are entered skilfully. Experiments prove that the form of 
objects is not clearly perceived, but that movements are; 
and the general conclusion is that sight is not of very great 
importance in the daily life of the creature. Touch and 
smell probably count for much, but habit for more 
still. The dancer learns to find its way quickly out of 
a maze, and when it has learned the trick it can follow 
the path apart from any trail and in the dark. In all 
probability a motor habit has been enregistered which 
can work without any immediate guidance from the 
senses. 

Of great interest are the experiments by which Professor 
Yerkes was able to prove the educability of the dancing 
mouse. Beside the cage, to take a simple case, he placed a 
wooden box, from which a ladder of wire netting led home. 
‘“A dancer when taken from the next-box and placed in 
the wooden box could return to its cage and thus find 
warmth, food, and company by climbing the ladder.” 
The results varied, showing marked individual differences 
in intelligence. The mouse called No. 1,000 learned to 
climb quickly, and largely by his own initiative. But 
those called No. 2 and No. 6 learned only by tuition, being 
put through the required act by Professor Yerkes. Some 
could not get out at all. One of these, called No. 5, was 
placed along with No. 1,000 in the box, but failed to profit 
in the least by repeated trips which No. 1,000 made for 
her benefit day after day. 

Unlike some other animals, the dancing mouse does not 
seem to profit by what its neighbours do. Imitation counts 
for almost nothing. By using the labyrinth method, it 
was found possible to measure the varying rapidity with 
which a habit can be formed and to test the durability 
of the habit when it has been acquired. We have not been 
able to do more than hint at the heights and depths of the 
inquiry into the peculiarities of the dancing mouse, but 


248 SCIENCE, OLD AND NEW 


we have perhaps said enough to show that it has already 
justified its existence by affording a most excellent subject 
for the scientific study of animal behaviour. It is no 
corpus vile! 


XXXII 


BIOLOGICAL DICHOTOMIES 


249 


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BIOLOGICAL DICHOTOMIES 


THROUGHOUT animate Nature we see bifurcations, 
many of which certainly depend on the see-saw of proto- 
plasmic metabolism, as that again depends on some deeper 
dichotomy till we get down, it may be, to the difference 
between positive and negative charges of electricity. In 
every living body there is building-up and breaking-down, 
synthesis and analysis, winding-up and running-down, 
anabolism and katabolism, repair and waste, assimilation 
and disassimilation, income and expenditure, and so on— 
for such is the fundamental antithesis of life from the 
chemical and physical, as well as from the common-sense 
point of view. A living creature, however simple, implies 
keeping a balance between the two sides and being a going 
concern, enduring for a longer or shorter time. But the 
fulfilment of this primal condition leaves room for many 
alternatives or organic dichotomies. 


Plants and Animals 


Very far back in the history of living creatures, antece- 
dent to the definite cleavage between plants and animals, 
there was a divergence between those organisms that fed 
at a low chemical level—on the primary constituents of 
the atmosphere, water, and its dissolved salts, and those 
organisms which could not utilize anything but complex 
nutriment previously manufactured. This was the pri- 
mary cleavage between the peaceful and the predatory, 


251 


252 SCIENCE, OLD AND NEW 


between feeding-low and feeding-high, between savers and 
spenders; and it expressed a dichotomy between the rela- 
tively more anabolic and the relatively more katabolic. 
An incalculably important step was made when plants 
acquired the green pigment chlorophyll, which made it 
possible for them to utilise more readily the energy of 
sunlight in their photo-synthetic activity which remains 
mysterious. Thus was established the deep cleavage 
between plants and animals, which differ from one another 
as munition works from active batteries. Green plants 
have extraordinarily preponderant anabolism; they make 
and store abundance of explosives which animals may 
eventually utilise. 


Saving and Spending 


Now, all through the evolution of animals, we can dis- 
cern the same forking of the ways; we see it in the contrast 
between a sluggish Sporozoon, such as the malaria para- 
site, and an intensely active Infusorian, such as the 
luminescent Noctiluca of all the seven seas; between the 
sedentary corals in their thick-walled castles of indolence 
and the free-swimming, aggressive Portuguese Men-of- 
War; between the fixed barnacle and the frolicsome shrimp, 
the limpet and the sea-butterfly, the ascidian and the 
salp, the tortoise and the eagle, the ground-sloth and the 
aérial bat. Of course all sorts of secondary adaptations 
have been in each case super-added, but to begin with 
there has been, as it were, a choice between two possible 
modes of life: the relatively anabolic and the relatively 
katabolic, the more conservative and the more adven- 
turous, the saving and the spending habit. 


Female and Male 


There has been recent experimental corroboration of the 
thesis of The Evolution of Sex (Geddes and Thomson, 1889) 


BIOLOGICAL DICHOTOMIES 253 


that the sex-divergence is an illustration of a widespread 
organismal dichotomy, that the female is an organism in 
which the ratio of anabolism to katabolism is greater than 
the corresponding ratio in the male. In other words, the 
sexes differ fundamentally in the rate and rhythm and 
routine of their metabolism, the females being the rela- 
tively more anabolic. In pigeons there appear to be two 
different kinds of eggs, usually produced in approximately 
equal numbers, but in this respect modifiable by conditions 
of age, season, and so forth. Now the eggs which have 
adopted a more anabolic régime, storing more abundant 
and valuable reserve products, develop into females, and 
the others into males. There are many indirect confirma- 
tions of this physiological theory of sex, which is not in- 
consistent with the view that the immediate index and 
trigger-puller of one sex or the other may be found in 
nuclear peculiarities (sex-chromosomes) in the germ-cells. 
But our immediate point is simply that the sex-antithesis 
may be but a special case of a still more widespread 
dichotomy. 


Tender and Tough 


Corresponding to the dichotomy between plants and 
animals, there is among animals, as regards diet, an 
analogous contrast between the soft-mouthed and the 
hard-mouthed, the tender and the tough. The soft- 
mouthed animals feed on the whole on microscopic or- 
ganisms, organic débris, and fine detritus, good examples 
being sponges, some corals, sea-cucumbers, feather-stars, 
earthworms and lugworms, acorn-shells and barnacles, 
oysters and other bivalves, ascidians, lancelets, and a few 
fishes. The hard-mouthed animals are predatory, and 
have something in the way of jaws, good examples being 
sea-urchins, Nereids, crabs, snails, and octopuses, most 
fishes, and all higher animals. And just as we thus divide 
animals into those that feed at a low level and those that 


254 SCIENCE, OLD AND NEW 


feed at a high level, so an analogous parting of the ways 
splits the latter into the pacific vegetarians and the pre- 
datory carnivores. 


Many-Celled and Single-Celled 


Another deep cleavage was between the unicellular 
and the multicellular mode of being, which Agassiz called 
the greatest gulf in organic Nature. The emphasis must 
not be laid on the difference in size, for size does not mean 
very much, and it is easy to find a single-celled (or non- 
cellular) animal far bigger than a Rotifer with a thousand 
cells, far bigger than a minute insect (with thousands of 
cells) which lands like a comma on our page as we read. 
Nor should the emphasis be laid on the difference in 
complexity, for while it may be true in a general way that 
unicellular animals are simple compared with multi- 
cellulars (Metazoa) from sponges to man, it is easy to 
find an Infusorian of extraordinary complexity. Think 
of Bellerophon, for instance, with its row of projecting 
turrets on each side, into which explosive capsules pass 
and are fired off when occasion requires! Every one of 
these minute animalcules is physiologically complete in 
itself; the life-histories are often so intricate that we find 
it difficult to remember the succession of chapters; the 
results of their architectural activity, whether with lime 
or flint produced inside of them, or with extraneous par- 
ticles collected from outside, are as beautiful as they are 
puzzling; and it is no figure of speech to talk of their 
‘‘mind.’’ We cannot very well say “‘higher”’ or ‘‘lower”’; 
they are on a different evolutionary tack; they illustrate 
a deep dichotomy, the interest of which is enhanced by 
their remarkable evasion of ‘natural death.” It may be 
that the difference between unicellulars and multicellulars, 
between organisms without a ‘‘body”’ and those with one, 
is an architectural, rather than a physiological, dichotomy ; 


BIOLOGICAL DICHOTOMIES 255 


but it is probable that the possibility of having a ‘‘body”’ 
with cells, tissues, and (eventually) organs, depended on 
a relatively anabolic period during which reserves were 
accumulated and dividing cells remained coherent instead 
of going apart in individualistic independence. 


Radial and Bilateral 


Another eventful parting of the ways was that which 
separated the bilateral from the radial animals. The radial 
symmetry of jellyfishes, polyps, and the like, which have 
no right and left sides, no definite head and tail, is well 
suited for easy-going, sedentary, or drifting life. But 
bilateral symmetry, beginning among multicellulars with 
‘“‘worms,’’ implies right and left, head and tail, and was 
better suited for a more vigorous life which commands its 
course, pursuing prey, avoiding enemies, and chasing 
mates. The establishment of bilateral symmetry was the 
beginning of our knowing our right hand from our left; 
it led to the establishment of head-brains and to a cephal- 
isation which only needed to be begun to succeed like 
success. The dichotomy between radial and bilateral 
animals was again architectural rather than physiological; 
but, while there are many notable exceptions, the majority 
of the radially symmetrical are sluggish, vegetative, and 
feeding low, while the majority of the bilaterally symmetri- 
cal are active, masterful, and feeding high. Itisinteresting 
to notice that the intensely active and luminescent Cteno- 
phores, like ‘‘sea-gooseberries”’ and ‘‘ Venus’s girdle, ’’ which 
are bipolar and incipiently bilateral, are all carnivorous. 
Some zoologists believe that it is among these Ctenophores 
that the origin of bilateral ‘“worms”’ is to be sought. 


Litile-Brains and Big-Brains—and Other Contrasts 


As we have seen, there are dichotomies which echo the 
primary contrast between relatively preponderant anab- 


256 SCIENCE, OLD AND NEW 


olism and relatively predominant katabolism, and there 
are others which imply the introduction of some new idea 
or principle. Among the latter we may further mention 
the divergence between ‘‘the little-brain type,”’ as Sir Ray 
Lankester calls it, rich in instinctive capacities but slow to 
learn, reaching its climax in ants, bees, and wasps, and 
“the big-brain type,” with a meagre endowment of in- 
stincts, but eminently educable, finding its climax in 
mammals and man. There is the contrast between ‘‘cold- 
blooded’’ animals, whose temperature approximates to 
that of the surrounding world, and the ‘‘warm-blooded”’ 
birds and mammals, which remain of nearly constant 
temperature. There is also the momentous contrast 
between animals that lay eggs hatched outside of the body 
and those that have a more or less prolonged and intimate 
symbiosis between the unborn offspring and the mother, 
recalling the relation of seed to parent-plant, and evidently 
pointing to anabolic reserves on the maternal side. We 
must refrain from trying to follow the biological dichot- 
omies into human life, where we see them in the contrast 
between the excitable and the phlegmatic, the sanguine 
and the placid, the adventurous and the cautious, William 
James’s ‘‘tender”’ and “‘tough,”’ which have, of course, to 
be correlated with conditions of blood-pressure, internal 
secretion, and metabolic routine. But one final suggestion 
we must be permitted. The occurrence of dichotomies is 
characteristic of animate Nature, and many human 
features, such as having two hands, two cerebral hemi- 
spheres, two eyes, two ears, and so on, probably incline us 
to a bilateral logic. Our dilemmas are two-horned; our 
answers are yea or nay. Experience teaches, however, the 
frequent validity of a via media, of compromise of the 
truth between two extremes. And, looking back over 
animate Nature, revising our impressions, we see that 
apparent dichotomies are often less absolute than they 
seem. There are many organisms that balance income 


BIOLOGICAL DICHOTOMIES 257 


and expenditure, closely and subtly, there are intermedi- 
ates between plants and animals, there are intergrades 
between the tough-mouthed and the tender-mouthed, 
instinct and intelligence are often subtly mingled, radial 
and bilateral do not exhaust the possibilities, many crea- 
tures are not wholly male or wholly female. As often as 
not the path of life shows trifurcation, not dichotomy. 


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XXXITI 


MANY INVENTIONS 


259 


iP nee ’ 





MANY INVENTIONS 


THERE is a quality of insurgence in living creatures that 
is often startling. It is true that some seek the line of 
least resistance, and drift into a parasitic or a saprophytic 
life of ease, but that is not characteristic. The majority 
show fight—the will to live, and to live in a particular 
way, which is oftener against the stream than with it. 
The insurgence is expressed in prolific multiplication; the 
river of life is always threatening to overflow its banks and 
it often does so. One of the British starfishes has two hun- 
dred million eggs. The same quality is expressed in the mul- 
titude of distinct species—twenty-five thousand backboned 
animals, quarter of a million backboneless animals. It is 
shown in longevity, in the centenarian tortoise and parrot, 
or in the Big Tree that was cut down at the age of 2,425 
years; in the conquest of space, the Arctic Tern occurring in 
the Antarctic circle; in the exploiting of inhospitable areas 
such as the dark abysses of the ocean; in the circumventing 
of the seasons, either actively like the swallows flying 
south or passively like the hibernating hedgehog; and in 
numberless other ways for which it is difficult to find the 
common denominator. Is it, as Spinoza hinted, that 
living creatures have a unique vital inertia, bound to 
express their nature in spite of discouragements, bound 
to persist in the line of their own being? In any case, 
what Goethe said is true, that it is characteristic of organ- 
isms to be always attempting the apparently impossible 

261 


262 SCIENCE, OLD AND NEW 


and achieving it. The ‘‘Challenger’’ explorers showed 
that there is no ‘‘deep,”’ even one that would engulf the 
whole of Mount Everest and show nothing, too deep for 
life. 


Inventiveness 


But there is another quality of organisms for which it is 
difficult to find a name—unless it be inventiveness. They 
have, indeed, sought out what look like inventions, but 
the familiar difficulty is that the capacity for these 
comes to be a racial possession at levels where we dare not 
suppose that we are dealing with deliberately thought-out 
devices. We shrink from the audacious generosity of 
naturalists who have spoken of the sagacity of the Venus’s 
fly-trap and the shrewdness of the Bryony which binds 
itself to the hedgerow with a spring-anchor and rides the 
storm in safety; but how are we to describe the brainless 
starfish’s life-saving surrender of a part, or the way in 
which a dismounted sea-anemone—no better endowed 
with brains—will attach itself to the leg of a hermit-crab 
and climb up on to the back of the shell, recovering a lost 
partnership? And if we say that the ploughboy recovers 
his seat intelligently while the sea-anemone does so re- 
flexly, we have to face the difficulty of the origin of the 
highly profitable partnership between the crustacean and 
the coelenterate. The hermit-crab who deliberately seeks 
a partner-anemone, and puts it on the back of his bor- 
rowed house, who adds a second and a third till he is 
masked, who removes his partners when he has to flit to a 
new house, who sometimes carries a partner on his great 
claw as if it were a weapon (and is it not richly provided 
with batteries of stinging cells?), has a fairly well-devel- 
oped brain, and his behaviour may be suffused with an 
appreciative awareness of what he is doing. But the 
sea-anemone is on a much lower level, without nerve- 


MANY INVENTIONS 263 


ganglia at all, and yet it is in some cases much more 
than acquiescent in regard to the partnership. Re- 
sponsiveness to the touch of the hermit-crab may have 
come to be engrained in its constitution, but it is difficult 
to think clearly of its racial establishment. 


Many Devices, Intelligent and Otherwise 


In spite of some criticism, we adhere to the statement, 
which is well documented, that moles store earthworms 
near their headquarters in the autumn, and that they bite 
off their heads, with the result that the larder—a last 
resource when the frost grips deeply—remains fresh and 
yet cannot creep away. To what extent the mole is 
appreciatively aware of what looks like a device, who can 
say’? The Sea-Swift, Collocalia, of the Far East, finds 
little material wherewith to build a nest on the walls of 
the caves; it makes one of consolidated saliva—the well- 
known edible bird’s nest. The Greek eagle lifts the 
tortoise to a height, and drops it on the rocks below, with 
the result that the almost invulnerable carapace is broken 
open; rooks do the same with fresh-water mussels and gulls 
with sea-urchins. Now, when we are dealing with 
creatures of high degree, with finely developed brains, it is 
quite legitimate to make the hypothesis that they are 
intelligently appreciative of their agency—a hypothesis 
to be proved or disproved, perhaps, by carefully-arranged 
experiment. But when we pass to lower Vertebrates with 
poorly developed brains, the cloud of difficulty becomes 
more dense. What are we to say of the New Guinea fish, 
Kurtus, which finds no suitable or safe place for the deposi- 
tion of the eggs, the outcome being that the male fastens 
them in a double bunch to a special bony hook on the top 
of his head, and carries them about till they hatch? What 
are we to say of the strange frog which Darwin found in 
Chili, where the male carries his small family in his internal 


264 SCIENCE, OLD AND NEW 


croaking sacs until they become miniatures of himself and 
escape? It is a quaint illustration of paternal care and of 
a self-denying ordinance, but is it intelligently inventive? 


Instinctive Inventions 


The difficulty increases when we pass to animals on a 
very different evolution-tack—that of insects and spiders. 
The tailor-ants, common in warm countries, make a shelter 
by drawing leaves together, and their co-operative hauling 
is admirable; their mandibles are their needles, if you like, 
but they have nothing to sew with; what does each do but 
take a larva in its mouth so that the silk secreted from the 
offspring serves as thread for the parents? A common 
harvesting ant of South Europe collects seeds of clover-like 
plants, lets them begin to sprout so that the tough en- 
velopes are burst, exposes them in the sun so that the 
germination does not go too far, takes them back under- 
ground and chews them into dough, and finally makes this 
into little biscuits which are dried in the sun and stored 
for winter use. What a brilliant idea—and yet it cannot 
be that !—is suggested by the semi-domestication of green- 
flies by certain species of ants, and what shall we say of 
the slaves which others bluff into service? Many white 
ants or Termites grow mushrooms in extensive, specially 
constructed beds of chewed wood, and some of the true 
ants show a similar habit. 

On wayside plants in early summer we see everywhere 
the frothy masses called cuckoo-spit, each made by a 
larval frog-hopper which whips a little sugary sap, a little 
ferment, and a little wax into a strange persistent foam, 
protective against enemies and against the heat of the 
sun, the creature literally saving its life by blowing soap- 
bubbles. Not far off, on a bare sandy patch, are the deep 
shafts sunk by the grubs of the beautiful green Tiger Beetle. 
The grub, with quaint somersault movements inside the 


MANY INVENTIONS 265 


shaft, thrusts the loose earth with great force into the 
walls, and beats them smooth. Eventually it fixes itself 
near the top of the shaft so that the roof of its head forms 
a trap-door. When an ant or some other small insect 
settles down on this living lid, the grub suddenly explodes 
like a jack-in-the-box, hurling its victim violently against 
the hard upper edge of the shaft-wall. The sucked body 
is afterwards jerked out. The world is full of these 
inventions. 


All Sorts of Devices 


How are we to understand the behaviour of one of the 
Digger Wasps which lays its eggs in a sunk shaft, and 
provisions this with paralysed caterpillars? While the 
hunting and storing are in progress, the wasp shuts the 
mouth of the shaft after each visit, but does so in a rough- 
and-ready fashion. When the larder is full, however, it 
seals the entrance with earth and makes a neat job of it; 
nay, it takes a minute pebble in its jaws and beats the 
earth smooth. Who said animals could not use tools? It 
seems that using the pebble is not part of the instinctive 
routine, but is an individual touch, probably with more 
vivid awareness than is associated with the rest of the 
agency. But the difficulty is to think of the origin of 
either the routine or the finishing touch without postu- 
lating intelligence or, at least, some appreciation of 
significance. 

The water spider, an aberrant member of a thoroughly 
terrestrial race, breathing dry air, has been led to explore 
and exploit the pools on the moorland. The female 
weaves a flat web on the bottom, mooring it by silk tent- 
ropes to the stones; she goes up to the surface, entangles 
air in her hair, comes down again, gets under the silk 
sheet, and presses off the quicksilver-like air-bubbles with 
her legs. She does this many times till the flat web is 


2606 SCIENCE, OLD AND NEW 


buoyed up like a silver cupola; and in that dry diving-bell- 
like nest the eggs are laid and the young are hatched. 
The impossible has been achieved. 

Spiders have no wings, but some small kinds are given 
to aérial migration! On a breezy morning, especially in 
autumn, they mount on posts and parapets and tall herbs, 
and, standing with their heads to the wind, give forth from 
their spinnerets multiple jets of liquid silk which harden 
instantaneously into threads of gossamer. When these 
are long enough, the wind tugs at them, and the spider lets 
go. It is borne with the help of its silken parachutes on 
the wings of the wind, disappearing like the boy in the 
Indian rope-trick. If the wind rises it can furl its sails, 
if it falls it can spread more; and when the threads have 
fulfilled their passive function and have sunk to the earth 
in thousands, we see a shower of gossamer. 

Observant visitors to the Riviera are familiar with the 
shafts sunk by trap-door spiders on wayside banks. The 
lid, often about the size of a franc, is flush with the ground 
and usually exactly like its surroundings; it fits with 
precision and works on a silken hinge. The shaft is 
smoothly plastered within, and sometimes there is a side 
shaft, with a silken portiére hanging over the entrance, 
into which the spider can retreat if an enemy gets into the 
shaft before she has shut the door. We say “‘she”’ be- 
cause the shaft is for egg-laying and the mother spider’s 
work. It is plain that there are many ‘‘ideas’’ here—the 
hinge, the concealment of the lid, the side-aisle, and so on. 
But in some kinds we see on the polished white internal 
surface of the lid three or four little holes close together, 
about the size of pin-pricks. What are these but holes for 
the spider’s claws so that she can draw the door quickly 
and firmly after her? And they must be made while the 
cleverly manipulated clay is still soft. This comes near 
invention. 

Thinking of the method of opening mussels by letting 


MANY INVENTIONS 267 


them fall from a height, we can credit the fine brain of a 
rook with a fair share of intelligence; perhaps enough to 
take advantage of a method which a chance fall disclosed; 
perhaps enough to devise the method and to keep it up as 
a tradition. We must remember how the thrush smashes 
the snail shells on its anvil in the wood. But when we 
come to creatures of the little-brain type, whose behaviour 
is mainly on the instinctive level, we must cease to think of 
intelligently-thought-out inventions. We must think, 
it seems to us, of a continual individual experimentation 
with new tendencies and aptitudes, or with slight improve- 
ments on previously established aptitudes. Life has been 
a long-drawn-out game of “‘testing all things and holding 
fast that which is good.”’ On our view, what happens at 
levels below what may be called intelligent learning and 
invention is briefly this: that in the germ-cells, which 
epitomise the past, novelties are of frequent occurrence, 
not ‘‘anyhow’’ novelties, but new departures more or less 
consistent with the past. These arise organically, of 
course, not by giving thought to the morrow, for that the 
germ-cells, at any rate, cannot do. But these germinal 
cards are put into the hands of the player, the embodied 
organism, mind-body and body-mind in one, and it is for 
the explicit organism to play them, to test them, and even 
to find the environing conditions where they are of most 
avail. It is in this way that the lower animals have 
profited by inborn inspirations never clearly thought out, 
and just as it may have taken a million years to fashion 
the feathers of birds, so it may have taken ten millions to 
endow the tribe of ants with their marvellous repertory of 
apparent inventions. 





XXXIV 


THE CALL OF THE SEA 


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THE CALL OF THE SEA 


THE Loggerhead Turtles are open-sea reptiles of wide 
distribution, especially in the Atlantic. Two or three 
stray specimens have been captured on British coasts. 
They are carnivorous and of no commercial value, but 
they are very interesting because of the obedience of the 
young ones to the call of the sea. The adults are pelagic, 
as we have said, but the young turtles are hatched on 
shore, where the mothers have buried the eggs in the sand. 
About the month of August or a little earlier, the fully 
formed youngsters escape from the egg-shells and the 
sandy nest and make for the sea; and there is no clearer 
instance of an inborn obligation. It has been recently 
studied by a distinguished American naturalist, Profes- 
sor G. H. Parker of Harvard, and his results are very 
interesting. 


An Inborn Obligation 


‘“To see a dozen of these newly hatched creatures, that 
have had no previous experience with the ocean, scramble 
toward it, notwithstanding that it may not be within the 
range of their vision, is a sight tiever to be forgotten. Any 
attempt on the part of an observer to check them in their 
course seems only to excite them to further effort which 
does not cease till they have reached the water. To the 
observer they seem to be drawn toward the sea by an 

271 


272 SCIENCE, OLD AND NEW 


influence as mystical as it is impelling.” This is the kind 
of problem that the biologist loves, to analyse the call of 
the sea. 

The first thing Professor Parker did was to put a newly 
hatched Loggerhead at the centre of a paper board about a 
yard square and surrounded by a low wooden fence about 
six inches high. He pointed its head north, but it went 
west. He took another one and pointed its head south, 
but it went west—literally, of course, we mean. He took 
a third and pointed its head east, but it went west. He 
took a fourth and pointed its head west, and it went west. 
The experiment continued, with one turtle at a time, and 
almost without exception they went west. Why was that? 
The water and the later afternoon sun were both in the 
west. 

The next step was to find out whether the sun or the 
water was the effective factor, and that was easily done 
by transporting the paper board and pen to the opposite 
shore of the narrow peninsula or Key in Florida where the 
experiments were made. Here the water was to the east 
while the sun not unnaturally remained in the west. The 
young Loggerheads all went east, which proved that their 
movements were related to the position of the water and 
not to the sun. 


Not Guided by Sight, Hearing, or Smell of the Sea 


“On my return from the ocean on the east side of the 
Key to the bay on the west side I stopped in a field about 
midway between the two bodies of water, and having set 
up the pen here with its floor horizontal, I proceeded to a 
third set of tests.” The result was that when the turtles 
were treated as before they were not disposed to move 
much from the centre of the board, and that when they did 
move they were as likely to go in one direction as in 
another. They were not hearing the call of the sea. 


THE CALL OF THE SEA 273 


Another fact soon emerged, that the young creatures 
are very responsive to the slope of the surface on which 
they move. They like going downhill, or, in more correct 
language, they are positively geotropic—at any rate after 
they escape from the shallow sand nest. So they will 
tend to go down the slope of the shore to the sea. Further 
experiments showed that they were not directed to the sea 
by the tang in the air, or by the humidity, or by the sound 
of the waves. When a shallow vessel of water was placed 
near the line of their seaward march they passed by with- 
out any deflection. 


Towards the Free Horizon 


But it was plain that there must be some directive 
influence, for when they were liberated in the pen in the 
darkness of night, they did not move towards the water 
as usual, but crept about indiscriminately. This sug- 
gested further experiments which led to the interesting 
conclusion that the newly hatched Loggerheads move 
away from any large mass that interrupts the horizon 
and move towards any considerable stretch of openness. 
From inside a tub, whence they could see only the over- 
head sky, they had no orientation. But from the top of 
an inverted tub, whence they could see all round, they 
directed their course for the sea. They did so, moreover, 
after moving round in a small tentative circle, as though 
testing the whole horizon and then following the line to- 
wards the greatest openness. They did not move towardsa 
light in a dark room, but they are unmistakably influenced 
by a complex impression of open horizon as distinguished 
from a more interrupted horizon. Professor Parker insists 
that they respond to the details of their retinal images 
rather than to these images as wholes. Dr. Hooker, who 
made good experiments some years ago, concluded that the 
young Loggerheads move in the direction of blue sky, and 


274 SCIENCE, OLD AND NEW 


Professor Parker does not exclude the probability that 
they move toward blue areas rather than toward those of 
other colours. He has shown, however, that the creatures 
will find their way without either blue sky or blue water. 

What then is our picture of the inborn susceptibilities 
of the newly hatched Loggerheads as they emerge in the 
daylight from the darkness or semi-darkness of the eggs 
and the sand? They are suddenly ushered into a world 
of which they have no experience and they exhibit an 
effective obedience to enregistered predispositions which 
are awakened by trigger-pulling stimuli. The first factor 
is that they will rather go down than up; and that works 
well. The second factor is that they move toward regions 
in which the horizon is open and clear, and away from 
those in which it is interrupted. This usually works well. 
And there may be a third influence that they tend to move 
towards blue, which may also work well. 

If we were in the Loggerhead’s place and in full pos- 
session of our faculties, we should sniff and listen, we 
should gaze all round and test the slope, and then would 
come profound reflection! But the Loggerhead does not 
reflect. Nor is it constitutionally bound to go toward the 
sea as a moth to the candle, or an earthworm to darkness. 
Its actions are inborn or instinctive reactions to partic- 
ular stimuli, but they have not the obligatoriness of what 
are called tropisms. A very interesting point is that 
when a Loggerhead was started near some high shrubbery 
which intervened between it and the sea, it always moved 
away from the shrubbery and towards the open field. 
This was of course ‘‘wrong,’”’ but it shows that after all 
the call of the sea (for the Loggerhead) is the call of the 
open horizon! What is it for us? 


XXXV 


THE BEHAVIOUR OF INSECTS 


275 





THE BEHAVIOUR OF INSECTS 


THERE is an American wasp that is fond of a black 
waterside spider several times larger than itself—or, 
more accurately, herself. The booty is paralysed, but it 
is too heavy to fly with, and the vegetation is too thick to 
allow of land transport by haulage. ‘‘Out on to the sur- 
face of the placid stream the wasp drags the huge limp 
black carcass of the spider and, mounting into the air with 
her engines going and her wings steadily buzzing, she sails 
away across the water, trailing the spider and leaving a 
wake that is a miniature of that of a passing steamer.” 
She makes straight for the burrow where her eggs are laid, 
she hauls the spider up the bank and drags it into the 
hole to form part of the provision for her young ones. It 
is this kind of almost incredible behaviour that fills us with 
amazement; it seems to belong to a different order of 
things from ours. As Maeterlinck said: ‘‘The insect 
brings with it something that does not seem to belong to 
the customs, the morale, the psychology of our globe; we 
cannot grasp the idea that it is a thought of that nature 
of which we flatter ourselves that we are the favourite 
children.’”’ But while we may never be able to understand 
ants, bees, and wasps, just because we are as character- 
istically creatures of intelligence as they of instinct, it 
should be possible to get nearer them than mere wonder 
brings us, and a great step towards getting things into 
order has been taken by Professor E. L. Bouvier in his 


277 


278 SCIENCE, OLD AND NEW 


Psychic Life of Insects, translated (1922) by Dr. L. O. 
Howard. 


Tropisms 


When the caterpillars of the Brown Tail moth are 
hatched from the eggs, the first thing they do is to climb 
up the twigs where they find themselves, and this brings 
them to the young leaves which they require for food. 
Similarly, the maggots of the bluebottle penetrate into the 
meat; the mature queens and drones in the bee-hive seek 
the light of day; ants retreat into their nests when it is too 
hot or too cold outside, and make straight tracks away 
from essence of pennyroyal; the male silkmoth is attracted 
to the fragrance of the female; some aquatic insects always 
swim against the stream and some flies always make their 
way against the wind. Now these activities are Tropisms, 
engrained constitutional obligations, in most cases adap- 
tive. An asymmetry of stimulus provokes asymmetry of 
muscular activity ; this automatically results in movements 
which restore symmetry of stimulus. Whatever may have 
been the case during the establishment of the tropism, it 
is eventually an engrained obligation, requiring no will or 
control, and without any verifiable psychic side. It 
should be noted, however, that one tropism may influence 
or counteract another, and that a tropism may change in 
character with the age and physiological condition of the 
animal. 


Engrained Rhythms 


Roubaud has described interesting ‘‘house-worms”’ 
from Africa, the maggots of a fly, which burrow during the 
day in the earthen floor of huts, but come up at night and 
gorge themselves on the blood of sleepers. A periodicity 
has been established in the body of these insects, and 


THE BEHAVIOUR OF INSECTS 279 


Roubaud was able to prove that they may be experi- 
mentally induced to come up by day or by night according 
as they are treated. This leads us on to rhythms en- 
grained in the constitution. Some moths are active 
by day and others by night, just as some flowers open 
by day and others by night. Some walking-stick insects 
are absolutely motionless during the day, but begin to 
explore whenever night falls. There are many internal 
Vital Rhythms which have been punctuated in reference to 
external periodicities; an organic memory is established 
which eventually provokes activities independently of the 
original stimuli. This is not as yet psychism, but it is on 
the way. 


“Differential Sensitiveness”’ 


The bed-bug hides from the light; this is its tropism. 
If it be accidentally exposed to the light, it immediately 
turns through 180 degrees; this is called its ‘‘differential 
sensitiveness.” It is very difficult to make a bed-bug 
which is on black paper pass over on to a piece of white 
paper. When the mourning-cloak butterfly is resting in 
the sunshine, it turns its back to the light; when it is walk- 
ing or flying it keeps its face the other way. If a shadow 
be thrown on it when it is walking, it stops, momentarily 
closes its wings, and then quickly takes flight. This is 
differential sensitiveness, when animals move away from 
situations which are unfavourable to the exercise of their 
normal tropisms. The sudden change provokes an 
opposite kind of activity which lasts for a time, after 
which there is a return to the former state or direction; 
and an important fact is that the sudden change, say a 
gust of wind, a warm breath, or altering the slope of the 
surface on which the insect creeps, may reverse the crea- 
ture’s behaviour in regard to some quite different kind of 
stimulation, such as light. 


280 SCIENCE, OLD AND NEW 


A well-known expression of differential sensitiveness is 
seen in cases of so-called ‘‘death-feigning.’”’ The reaction 
to the sudden change is abrupt immobilisation. Many a 
beetle suddenly seized becomes instantaneously rigid 
and may remain in this condition, though no longer 
molested, for half an hour. In some cases the muscles 
pass into a tetanic state, so that a big insect like a water- 
bug can be held out stiffly by one of its slender legs. In 
higher animals the catalepsy may sometimes have pro- 
tective value, but among insects it rarely admits of any 
utilitarian interpretation. It appears to be an exag- 
geration of differential sensitiveness. 


The ‘‘ Trial and Error”? Method 


So far, then, in tropisms, vital rhythms, and differential 
sensitiveness there is little indication of any mental 
aspect. Of that the first clear evidence is to be looked for 
when the creature tries one reaction after another and 
selects that which is most satisfactory (the ‘‘trial and 
error’? method), or when it illustrates “‘learning,” which 
involves individual associative memory. A wasp 
struggles ingeniously to get its booty over obstacles; a 
mortar-bee searches for the shifted snail-shell in which it 
has laid its eggs, and having found where we have put it 
retains amemory of the place; a cockroach can be taught 
by electric shocks to avoid a dark passage in its cage; the 
sacred scarab that makes balls of dung alters its behaviour 
according to the nature of the soil; the solitary urn- 
making wasp Ammophila closes its nest perfunctorily 
so long as it is not fully provisioned, but when the labour 
of collecting food for the future larve is over, there is a 
careful blocking of the door and smoothing of the surface. 
In some cases a little pebble is used as a pounding instru- 
ment. Here we see individuality, alternatives, some 
appreciation of means and ends. 


THE BEHAVIOUR OF INSECTS 281 


Instinctive Behaviour 


The next level of behaviour is instinctive. It includes 
the innate and automatic capacities of the creature as a 
whole, a chain of doings which are individually like reflexes 
but have a psychic as well as a physiological concatenation 
—‘‘automatisms dominated by cerebral activity.” In- 
stinctive behaviour tends to routine, and yet it is often 
variable; it is not the result of lapsed intelligence, and yet 
it tends to become more and more automatic. According 
to Bouvier, one can hardly see in insects ‘‘simple reflex 
machines,’’ as some mechanists have called them, ‘‘for 
they know how to bend to circumstances, to acquire new 
habits, to learn and to retain, to show discernment. 
They are, one may say, somnambulists whose minds 
awaken and give proof of intelligence when there is need 
for it.”’ But when the instinctive behaviour is most 
perfect, and seems almost rational, it is probably most 
divergent from intelligence. ‘‘Never are the insects so far 
from us as when they appear to resemble us most.” 

Bouvier is neither Lamarckian nor Weismannist, but he 
inclines to the former more than to the latter. New 
departures in instinctive behaviour may arise like mu- 
tations from some germinal change, but their testing and 
establishment may require intelligence, and new habits 
intelligently acquired may add to the patrimony of instinct. 
There is no faculty of “‘instinct”’; different forms of in- 
stinctive behaviour may arise in different ways; instinctive 
and intelligent behaviour are not of the same order, yet 
they assist one another at many a turn; they are both 
‘opposites and complements.’’ And the fact that in- 
stinctive behaviour reaches its climax in insects and other 
arthropods is correlated with their particular type of 
body-architecture, with a chitinous exoskeleton and the 
muscles inside, with numerous specialised appendages 
which are like organic tools—usable in certain ways and 


282 SCIENCE, OLD AND NEW 


not otherwise. The specialised mouth-parts of a bee are 
the antithesis of man’s generalised hand, which is able to 
do any kind of work, and with this is associated the fact 
that the bee is predominantly instinctive and man 
intelligent. 


Intelligent Behaviour 


But let us complete our ascent of the inclined plane of 
insect behaviour by citing a case where we should say that 
intelligence takes the reins. There are predatory wasps 
called Pompilids that hunt spiders and are very diverse in 
their behaviour. There is one kind that follows a trapdoor 
spider down her shaft and stings her there. But in the 
autumn this spider makes a side shaft with a separate 
door on the surface of the soil, and this makes capture 
more difficult. What does Pompilus do? One trick is to 
carry away the two doors, for this induces the spider to 
come up to repair the damage. Another trick is to stick 
its tail into one of the doors and then withdraw quickly to 
watch the other. If nothing happens, the wasp does the 
same thing at the other door. A third trick is to give 
certain knocks at one of the doors, at the same time watch- 
ing the other. The spider eventually jumps out, a crea- 
ture of great agility, but the wasp is quicker still! It does 
not seem too generous to call this kind of behaviour 
Intelligent. 


XXXVI 


SENSITIVE PLANTS 


283 


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SENSITIVE PLANTS 


COMPARED with most animals, plants seem to live a very 
sleepy life. They doa great deal of work, especially in the 
manufacture of chemical explosives and in raising a mass 
of foliage against gravity, but it is done in a dreamy sort of 
way. So it seems at least, but we can only guess at the 
inner life of plants, not knowing how to put ourselves 
en rapport with them. Perhaps it may be said that we 
know more about the chemistry and physics of plants than 
about their biology, and that of their psychology we know 
nothing. This being so, it is of great interest to study 
plants when they awaken a little to agency, when they 
bestir themselves to answer back in visible movement. 


Movements of Plants 


How often we have sat on the dry hillside where the 
rock-roses (Helianthemum) spread out their flowers in the 
blaze of the sunshine, closing up when a cloud comes, and 
touched the central crowd of stamens with the tip of our 
little finger to see them all bend outwards to the periphery. 
There is something pleasant in knowing that this move- 
ment takes place naturally when the stamens are stimu- 
lated by the legs of the appropriate insect-visitor, and that 
dusting with pollen is thereby affected. But there is 
another pleasure in following the deliberate outward 
movement, which only occurs in the warmth of the sun. 
It brings the plant nearer to us, this answer-back. ‘The 

285 


286 SCIENCE, OLD AND NEW 


same sort of wakening up is seen when we touch with a 
bristle the inner side of the base of the stamens of the 
barberry in the hedge or the related Mahonia in the garden 
—there is a movement inwards to the pistil. How often 
we have lingered by the side of the stream to touch 
with a hair the bilobed stigma of the golden Mimulus, to 
see it close its lips. There is something pleasant in the 
fitness of the movement, for in natural conditions it 
serves to make sure of the pollen grain which has landed 
between the lips; but there is here also another pleasure, a 
glimpse of the unity of life, the touch of Nature that makes 
the whole world kin. 


Carnivorous Plants 


The margins of the glistening leaves of the butterwort 
(Pinguicula) curl in a little on the captured insects, and a 
similar response reaches a very high degree of perfection in 
the well-known Venus’s fly-trap of the peat-bogs of North 
Carolina. The bilobed blade of the leaf bears, on each 
half, three sensitive jointed bristles which stand up 
vertically. When these are touched (the trigger has often 
to be pulled twice) the two halves of the leaf fold quickly 
together, and the marginal teeth interlock like those of a 
rat-trap. Then follow the processes of secretion, digestion, 
and absorption that make this fly-trap so like an animal’s 
stomach. There are many suggestive details, such as Sir 
John Burdon Sanderson’s discovery that the closing 
movement of the leaf is accompanied by an electrical 
change similar to that associated with the contraction of 
animal muscle. But there is perhaps an even subtler 
suggestion in the fact that if the fly-trap is cheated several 
times in succession with useless touches, e.g., of pieces of 
paper, which bring no booty, it refuses for a brief period to 
answer back. This looks like the dawn of memory, and if 
it is, it matters little that the fly-trap’s memory should be 


SENSITIVE PLANTS 287 


avery short one. We do not need to go to Carolina to get 
a striking example of a plant’s power of answering back, 
for the sundew on the bog-moss carpet is all that we could 
wish. Its leaves are covered with ‘‘tentacles,”’ each witha 
viscid drop onits tip. When an insect gets a leg entangled 
in the secretion and begins to struggle, other tentacles 
are stimulated and more juice is exuded. As the news 
travels through the leaf all the tentacles curve inwards and 
close down upon the victim. Secretion of a peptonising 
ferment follows and then digestion and then absorption; 
after a while the leaf returns to the normal state of expect- 
ancy. We have repeated Darwin’s experiments showing 
how exquisitely sensitive the tentacles are to the least trace 
of a nitrogenous salt in a drop of water. 


Movements of Leaves and Flowers, Shoots and Roots 


One of the reasons for the relative sluggishness of plants 
is that the protoplasm of the vegetable cell is encysted by 
its cell-wall of cellulose. Like the medizval knight, as has 
been aptly said, its movements are checked by its pro- 
tective armour. And yet, in addition to the cases we have 
referred to, how much mobility there is, especially in 
young and actively growing parts. As Darwin first noted, 
the tip of the growing seedling moves slowly round, bend- 
ing and bowing to the different points of the compass, and 
roots move as well as shoots. Leaves rise and fall, flowers 
open and close, with the waxing and waning light of day, 
and tendrils are exquisitely sensitive to the touch of the 
support round which they coil themselves. When we add 
everything up, plants are much less stationary than 
they seem. 

Professor F. O. Bower’s Botany of the Living Plant 
(1923) gives us very vividly the impression of plants as 
living creatures—struggling for food and light and foot- 
hold, growing and moving, feeling and answering back, 


288 SCIENCE, OLD AND NEW 


overcoming difficulties and establishing inter-relations, 
multiplying and developing, varying and evolving, making 
the dry land their kingdom and opening the way to the 
higher, more wakeful, life of animals—especially terrestrial 
animals. ‘The same impression is reached along a different 
path in Sir J. C. Bose’s Life Movements in Plants, the 
latest of a remarkable series of studies on the irritability of 
living creatures. In a general way it may be said that 
this distinguished investigator has shown the plant to be 
much more responsive than botanists had suspected and 
much nearer ourselves than we had dared to believe. 
“Investigations which I have carried out show that all 
plants, even the trees, are fully alive to changes of environ- 
ment; they respond visibly to all stimuli, even to the slight 
fluctuations of light caused by a drifting cloud.”’ 


The ‘‘Praying”’ Palm of Faridpur 


It is a pretty story that he tells of the ‘‘Praying”’ palm 
tree of Faridpur, though it is, as it were, only a picture in 
his book. ‘The date palm in question, which has died of 
too much publicity, used to prostrate itself every evening, 
when the temple bells called the people to prayer. It 
erected its head in the morning, and so every 
day of the year to the admiration of the pilgrims. 
Some storm had probably displaced it from the ver- 
tical to an inclination of about 60° thereto, and it 
was this that made it bend and bow so emphatically, the 
highest part of the trunk moving up and down through 
over a yard. The large leaves that pointed high up 
against the sky in the morning were swung round in the 
afternoon through a vertical distance of about six yards. 
‘To the popular imagination the tree appears like a living 
giant, more than twice the height of a human being, which 
leans forward in the evening from its towering height and 
bends its neck till the crown of leaves press against the 


SENSITIVE PLANTS 289 


ground in an apparent attitude of devotion.’’ In such 
a sentence we feel the Oriental atmosphere, but there is 
nothing of this in the rigorous analysis with which Sir J. C. 
Bose showed that the phenomenon of the ‘‘Praying’’ palm 
is exhibited, more or less, by all trees and their branches, 
being in fact an illustration of the well-known modifying 
influence of temperature on geotropic curvature. The 
tree, apparently so rigid, behaved like a gigantic living 
cushion (like the pulvinus at the base of the leaf of the 
sensitive plant) in responding to the diurnal rise and fall 
of temperature. ‘‘The movement of the ‘Praying’ palm 
is a thermonastic phenomenon.”’ ‘There is no mistaking 
the melodious voice of science. 


The Sensitive Plant 


Many of us have played with the sensitive plant 
(Mimosa pudica), which takes up its sleep position (though 
not its sleeping condition) when it is touched. Each of 
the beautiful leaves has four parts or pinne bearing 
crowded leaflets on each side; at the base of each leaflet, of 
each of the four pinne, and of the main leaf-stalk itself 
there is a motile organ or pulvinus; and all the movements 
are due to changes in the turgidity of the cells of these 
cushions. If we hold a lighted match near some leaflets 
of one of the pinne they fold quickly upwards, the message 
passes to other leaflets and they follow suit, it travels 
to other pinne and their leaflets fold up, the four petioles 
draw together like a closing umbrella, and suddenly (when 
the news arrives) the main leaf-stalk sinks down. Haber- 
landt has shown that the stimulus travels by special 
elements in the bast of the vascular bundles of the leaf. 

Now, it is to this attractive exhibition of sensitiveness 
and mobility, and to analogous vitality in other plants, 
that Sir J. C. Bose has given his patient and ingenious 
attention for many years. He shows us, for instance, that 


290 SCIENCE, OLD AND NEW 


the lower half of the cushion of the sensitive plant is eighty 
times more sensitive than the upper, and that the fall of 
the leaf is due to the predominant contraction of the more 
excitable lower half; that the excitability of the plant 
varies throughout the day according to changes of 
temperature and light; that the plant may suffer from 
depression and shock, fatigue and ageing, and that it may 
be refreshed by rest and stimulants; and that the answers 
it gives depend not a little on the ‘‘tone’”’ of the tissues at 
the time. We feel how wise Linnzus was in uniting plants 
and animals under the title ‘‘Organisata.” 


The Crescograph 


One of Sir J. C. Bose’s truly admirable contrivances is 
called the crescograph, which records automatically and in 
magnified expression the growth of plants and its varia- 
tions under different treatment. With growth-measurers 
(auxanometers) previously in use a magnification of 
about twenty times was secured, but it took nearly four 
hours to determine the influence of changed conditions on 
growth. The crescograph gives a magnification of ten 
thousand times or more, and reduces the necessary period 
for experiment to thirty seconds! So may be studied 
the influence exerted on growth by temperature, chemical 
excitants, anesthetics, poisons, increase of turgor (induced 
by irrigation with cold water and with warm), electric 
stimulation (often below human perception), light (which 
antagonises warmth), and other factors in the environment. 
It has been suggested that the crescograph will advance 
practical agriculture, ‘‘since for the first time we are able 
to analyse and study separately the conditions which 
modify the rate of growth. Experiments, which would 
have taken months and might thus have their results 
vitiated by unknown changes, can now be carried out in 
a few minutes.”’ 


SENSITIVE PLANTS 291 


It was in 1878 that Claude Bernard published his 
famous book, Phénoménes de la Vie Communs aux Ani- 
maux et aux Végétaux: how it would have delighted him to 
know that the speed with which excitations pass through a 
plant has been measured; that plant excitability and the 
variations of it have likewise been measured; that there is 
periodic insensibility in plants corresponding to what we 
call sleep; that vegetable tissues show like animal tissues 
the effects of stimulants, anesthetics and poisons; that 
a death-spasm takes place in the plant as well as in the 
animal. It is not a useful expenditure of time to try 
to show that different kinds of things are the same; and 
animals are very different from plants when all is said and 
done; but it is a fine disclosure of the essential unity of 
animate Nature that we owe to the insight, patience, and 
manipulative skill of Sir Jagadis Chunder Bose. It is in 
accordance with the genius of India that’ the investigator 
should press further towards unity than we have yet hinted 
at, should seek to correlate responses and memory im- 
pressions in the living with their analogues in inorganic 
matter, and should see in anticipation the lines of physics, 
of physiology, and of psychology converging and meeting. 


The thrill in matter, the throb of life, the pulse of growth, 
the impulse coursing through the nerve and the resulting 
sensations, how diverse are these and yet so unified! How 
strange it is that the tremor of excitation in nervous matter 
should not merely be transmitted but transmuted and reflected 
like the image on a mirror, from a different plane of life, in 
sensation and in affection, in thought and in emotion! Of 
these which is more real, the material body or the image which 
is independent of it? Which of these is undecaying, and which 
of these is beyond the reach of death? 


Here, no doubt, reach exceeds grasp, but that is as it 
should be. 









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AXXVII 


THE COLOUR OF TROUT AND OTHER FISHES 


293 





THE COLOUR OF TROUT AND OTHER FISHES 


WHEN we watch trout in a stream, perhaps from a low 
bridge, we rarely detect more than flitting shadows. 
When we look at them in an aquarium or just after capture, 
we realise their great beauty, though it is admitted, of 
course, that they differ greatly according to their habitat, 
food, and idiosyncrasies. The same trout may be brilliant 
at one time and distinctly off colour at another. Accord- 
ing to the British Museum expert, Mr. Tate Regan, the 
typical coloration is something like this :— 


The colour of the back varies from bluish grey or bright 
olive through different shades of green, yellow, brown, and 
violet to nearly black; the sides usually have silvery or golden 
reflections, and the blues of the back are replaced below by 
white, yellow, or grey. The spots, black, brown, or red, 
stellate, round or oval, and often ocellated, differ greatly in 
their size, number, and distribution. 


In a large lake with pebbly bottom the trout are very 
silvery; in peaty water against a rocky bottom they are 
often very black; the mollusc-eating ‘‘Gillaroo”’ is often 
true to his name, which means ‘‘red fellow’’; and there are 
many other diversities, to the significance of which we 
shall afterwards refer. But everyone will allow that a 
typical trout is a very beautiful fish. 


Different Styles of Coloration 


It is invidious to compare different kinds of coloration 
among animals; they are like the styles of different paint- 
295 


296 SCIENCE, OLD AND NEW 


ers. But there is a peculiar charm, we think, in the colours 
of fishes; and it is not confined to those we ourselves catch. 
In the wonderful brilliance of humming birds and birds of 
paradise and the peacock’s tail, or in the witchery of many 
butterflies, we have to deal with static precipitates of 
pigment, enhanced by the physical structure of the 
surface of the feather or scale with its fine lamine or 
gratings which cause iridescence. But in fishes (and in 
cuttlefishes) the coloration is mainly due to actively living 
pigment cells or chromatophores. We think that a pecu- 
liar subtlety is naturally enough due to the pigment being 
bound up with the protoplasm which ebbs and flows in 
restless tides within the chromatophores. The same sort 
of pigment cells are found, it is true, in frogs, chameleons, 
and their relatives, which appeal less strongly to the lover 
of colour, but their relative inferiority may be due to the 
fact that fishes are aquatic animals, and can therefore 
allow themselves greater artistic liberty than is usually 
permissible for creatures living on land. Moreover, 
when we study an ASsop prawn among the seaweed, a 
crustacean with an extraordinary repertory of colour 
changes, we see the same liquid colour that we admire in 
fishes, and here again we have to deal with intensely living 
chromatophores. 

It will be understood that we are not saying that a 
mackerel has finer colouring than a milkmaid, or that a 
coral-fish, like a fragment of a rainbow, excels a cockatoo. 
Such statements have little meaning. What we say is 
that there is a difference in style between coloration due to 
static factors (pigment fixed in a matrix that dies, but 
often enhanced by a finely lined or laminated surface), and 
coloration due to kinetic factors (pigment borne by the 
restless living matter of expanding and contracting chro- 
matophores). A third style is familiar in many flowers 
where the colouring matter is dissolved in the cell-sap, 
forming coloured fluid in short. 


THE COLOUR OF TROUT AND OTHER FISHES 297 


Colour Cells 


The colour of the trout is due mainly to numerous 
irregularly-shaped, very mobile, cells, containing pigment. 
These chromatophores belong to the under-skin or dermis, 
but they may lie between it and the outer skin or epider- 
mis. The latter is a very delicate transparent layer, like 
wet tissue paper, and comes off on our finger and thumb 
when we lift the fish. The scales, it may be noted, are 
dermic products, unlike the epidermic scales of snakes and 
tortoises. They lie in pockets of the skin with only a part 
protruding, over-lapping one another like the slates on a 
roof but much more so. The pigment-cells occur both 
above and below the scales. ‘Their peculiarity is that they 
contract and expand, and that they show numerous 
radiating processes of their living matter. In fact they 
are like very irregular amoebe. Sometimes a chro- 
matophore is greatly spread out with the pigment much in 
evidence; sometimes it is contracted down to a biconvex 
pinpoint, and, if this is general, the ground-colour of the 
trout is dominant. Any rapid change of colour in a fish 
is due to the expansion or contraction of the chro- 
matophores, or also to a change in their position in the skin. 
A slow change of colour is due to an increased accumu- 
lation of pigment in the cells, or to the assumption of 
pigment by cells previously colourless, or to a destruction 
of pigment-cells by hungry neighbours. There is no use 
trying to make things simpler than they are. 

In some trout, as in salmon, the flesh has a pinkish 
colour, which is due to oily globules tinged with a ruddy 
fat-pigment or lipochrome. But we may leave this flesh- 
colouring out of account, and keep to the pigments in the 
chromatophores. Here we have to distinguish between 
the dark-coloured melanins and the lipochromes, which 
show some shade of red, orange, or yellow. Ina goldfish 
we see how the ruddy lipochrome has got the upper hand 


298 SCIENCE, OLD AND NEW 


of the melanin. Whatever be their colour, the pigments 
are by-products of the chemical routine or metabolism of 
the fish, and it should be noted that there are numerous 
melanophores that never see the light of day. Thus they 
occur abundantly on the lining membrane of the body- 
cavity or in the envelope surrounding the brain. The 
melanin of the trout has the form of extremely minute 
dark particles, and it is practically certain that these 
represent waste-products due to the breaking down of 
protein material. They form part of the ashes of the 
living fire. 


Silveriness 


But there is another factor in the trout’s coloration— 
namely, the presence of cells (iridocytes) containing 
minute crystal-like spangles of a waste-product called 
guanin. The reflection of light from these spangles 
produces the silvery sheen so characteristic of fishes, and 
here again the creature gets ‘“‘beauty for ashes.” The 
glistening iridocytes occur especially in a delicate mem- 
brane on the under-surface of the scales, and it may be 
noted that the scales of some fishes are utilised in the 
manufacture of the frankly artificial Roman pearls. The 
guanin may also occur on the wall of the body-cavity and 
swim-bladder; and the familiar silveriness of the down- 
turned (right or left) side of flat fishes of the sole and 
flounder tribe is due to the absence of pigment and the 
abundance of guanin. In association with the chromato- 
phores the iridocytes add greatly to the beauty of the 
fish, for they produce a metallic shimmer or even rainbow- 
like iridescence. A well-known Californian species which 
has been introduced into some British lakes and rivers is 
called the Rainbow Trout. 

Some very interesting experiments on the colour of trout 
have been made by a Swiss zoologist Murisier. He found 


THE COLOUR OF TROUT AND OTHER FISHES 299 


that trout reared in an aquarium with a white bottom or in 
total darkness are light in colour, the dark chromatophores 
or melanophores being contracted. But sister trout 
reared in an aquarium with a dark bottom or in one with 
feeble illumination (partial darkness) are of sombre colour, 
the melanophores being expanded. He found that the 
contracted state of the melanophores is due to the acti- 
vation of a special nerve-centre in the brain, and this 
activation may be brought about either by a luminous 
excitation of the upper part of the retina by light re- 
flected from the white bottom, or by the absence of any 
retinal excitation in complete darkness. On the other, in 
dim light or in light that stimulates only the lower part of 
the retina (an absorbing bottom) the nerve-centre is 
affected in such a way that the melanophores are main- 
tained in a state of expansion, and the trout are dark in 
colour. The conditions of illumination do not affect the 
colour-cells directly, they operate circuitously through 
the eyes and the central nervous system. Eventually, of 
course, the orders reach the pigment-cells through the 
nerve-endings in the skin. To sum up: on a dark bottom 
or in dim light, trout are dark, with expanded melano- 
phores. Ona light bottom or in total darkness, trout are 
light, with completely contracted melanophores. We are 
afraid to trench on the question of blind fishes, for it is 
puzzling; but we may say that here also the nerve-centres 
are the controlling agencies. In total darkness blind trout 
behave like normal trout; that is to say, they turn light. 


Slow Changes of Colour 


From the Natural History point of view the slow change 
of coloration in trout is not less interesting than the quick 
change; both suggest the possibility of useful adaptation 
to surroundings. Murisier has shown that on a dark 
bottom or in relative darkness there is increased deposition 


300 SCIENCE, OLD AND NEW 


of black pigment, which may perhaps make the fish more 
invisible than usual. On a light bottom, as in the clear 
' water of shallow streams flowing over gravel, there is a 
relatively feeble formation of black pigment, and this 
again may be useful. And what is true of the amount of 
black pigment deposited holds in regard to the number 
of colourless cells that turn into melanophores. There 
are several reasons, however, why we must not attach 
too much importance to these utilitarian considerations. 
In the first place, the coloration is a by-play of the 
fundamental chemical routine, and perhaps its primary 
significance is simply as a non-utilitarian expression 
of individuality and idiosyncrasy. Secondly, we must 
remember that the coloration is affected not only by the 
amount of light, but also by the temperature, the oxygena- 
tion, the chemical composition of the water, and the food. 
It is a complex resultant, and perhaps it may also be 
influenced by the crossing of different races of trout. 
Thirdly, a trout in total darkness shows arrest of black 
pigmentation, just as a trout does on a light bottom. 
But if we attach much utilitarian significance to the light 
colour of the trout on the light bed of the stream, what 
have we to say as to the light colour of trout reared in total 
darkness? This can hardly be regarded as adaptive. 
For total darkness must be a very rare natural habitat for 
a trout; and if it were common, it would not be profitable 
for the trout to be light! Finally, we cannot but ask 
whether the variably coloured trout may not be credited 
with a capacity for selecting the environment where it is 
physiologically most comfortable, which may also be that 
in which it is safest. 


Colour-Change in Other Fishes 


Passing from the trout, let us inquire into colour-change 
in other fishes. We must probe a little further into the 


THE COLOUR OF TROUT AND OTHER FISHES 301 


anatomical details. Fine nerve fibres are in connection 
with the chromatophores, and when these are stimulated 
there is condensation of the pigment in the cells. In the 
medulla oblongata of the brain there is a nerve-centre that 
has to do with the colour-change and the messages travel 
for some distance down the spinal cord, then into the 
sympathetic system, and thence to the skin. Thus the 
coloration is under nervous control. Local stimulation 
sometimes causes change of colour in the skin, but in most 
cases the message comes from the brain. The importance 
of this nervous control is obvious. Within certain limits 
the fish can change its colour, and it does so in response to 
diverse stimuli—the colour of the ground, the colour of the 
light, the temperature of the water, and so on. In ordi- 
nary cases, adjustment to suit the colour of the ground does 
not occur in blind fishes; in other words, the colour of the 
surroundings first effects the eye. But a fish may change 
its colour during mental excitement, as Frisch has proved 
for the minnow, and a blind fish shows this as well as one 
with its vision unimpaired. 


Uses of Coloration in Fishes 


There are at least four uses that the coloration of fishes 
may have—(1) protective, (2) aggressive, (3) repellent, 
and (4) attractive. But which, if any, of these uses a 
particular fish may illustrate cannot be determined except 
by experiment, and there have been too few experiments. 
Nothing is more unsatisfactory than the facile assumption 
that an interpretation which works well in theory is 
therefore true to nature, or can be imposed by analogy 
from one case proved to a score not even tested. That is 
not the way in which secure science grows. (1) It has 
often been observed that some kinds of fishes can put on a 
veritable garment of invisibility. With a young plaice 
in a shore-pool one can demonstrate this, and repeat some 


302 SCIENCE, OLD AND NEW 


of the fine experiments made by Professor Sumner, who 
put flat-fishes on a great variety of artificial backgrounds 
and photographed the stages of assimilation. ‘They liter- 
ally fade into their surroundings as if the eye kept sending 
messages to the brain, and the brain to the spinal cord, and 
the spinal cord to the sympathetic system, and that to the 
peripheral nerves, and these to the chromatophores until a 
harmonious adjustment is arrived at. We believe that 
we are here very close to a great psycho-biological secret, 
and, in any case, there are two very noteworthy facts—the 
nicety of the colour adjustment when it is feasible at all, 
and the rapidity with which it is sometimes accomplished. 
In some of Professor Sumner’s experiments the flat-fishes 
succeeded in approximating to a pattern like a draughts- 
board. In some Australian fishes, of which Mr. David G. 
Stead has told us, the harmonisation is achieved in the 
course of a minute or two. But we must not assume 
without proof that the wonderful adjustment is an 
adaptation wrought out by natural selection because of its 
protective value. That the fading into the environment 
is of life-saving importance must be proved in each case. 
(2) A second possible utility, perhaps illustrated by the 
angler or fishing frog, is that the inconspicuousness may 
enable the fish to get its prey more successfully. The 
Gyges ring may be used not to ensure safety, but to secure 
sustenance. It may have aggressive value. (3) It has 
been satisfactorily proved that some fishes, from the 
minnow of our streams to the grey snapper of the coral 
reefs, have a definite colour-sense. They can discriminate 
colours, and form associations with colours, and retain 
these associations in their brains, poorly developed as 
these are. It is, therefore, quite possible that a brilliant 
colour may be of use as a warning advertisement, testifying 
to all whom it may concern that this fish should be left 
severely alone. There is a considerable body of evidence 
that some unpalatable or poisonous fishes, e.g., the weaver, 


THE COLOUR OF TROUT AND OTHER FISHES 303 


get on better because of their conspicuous colours, which 
have rivetted a noli-me-tangere impression in the minds 
of the predacious. (4) The fourth possibility is well 
illustrated by the male sticklebacks in the shore-pools. 
At the pairing season they are transfigured; they are living 
jewels of blue and red. It is quite possible that this may 
render the males more attractive in the eyes of their mates, 
whom they coax to enter the nest of seaweed they have 
fashioned. It is certain that a minnow, for instance, can 
discriminate between certain colours; it has been proved 
that some fishes can establish a definite association 
between a particular colour and something they like. 
Therefore it is quite possible that the brilliant male 
sticklebacks, and, still more, the males of the gemmeous 
dragonet which display their beauty elaborately, have 
their distinctive coloration justified by its value in mating. 
But definite proof is lacking. Would a male stickleback 
be less successful in khaki? 


Non-Utilitarian Colours 


But there are many fishes for whose brilliant coloration 
no utility is known. ‘This is well illustrated by the coral- 
reef fishes of the Tortugas, the subject of an admirable 
study by Professor Jacob Reighard, of the University of 
Michigan. The fishes are very conspicuous, in no way 
hidden from their enemies or from their prey. The 
coloration is the same in the two sexes, and it is not an 
advertisement of unpalatability. Reighard found that 
the grey snapper, a predacious fish of the reefs, which 
discriminates certain colours, forms associations readily, 
and has a memory, made no bones about devouring twenty 
species of the brilliant coral fishes. What then is the 
explanation? Reighard’s conclusion is that the brilliant 
colours are of no use at all. The fishes in question are 
very agile and very safe in the intricacies of the reefs. 


304 SCIENCE, OLD AND NEW 


Like humming-birds they have few enemies, and they have 
let conspicuousness run riot. The coloration is an ex- 
ternal expression of the intensity of the vital processes 
and in the immunity of the organism from the action of 
selection on its colour characters, it has become exuberant. 
We believe that this idea must apply to many cases where 
the often too ingenious utilitarian interpretations of 
colouring have broken down. 





XXXVITI 


LIVING LIGHTS 


395 






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LIVING LIGHTS 


ARISTOTLE speaks of the luminescence of dead fishes and 
damp wood, which we know to be due to bacteria and 
fungi respectively, but long before Aristotle the fishermen 
must have noticed that the oars sometimes drip sparks 
and that the breaking waves may gleam with light. In 
warm countries the bush aflame with fireflies must have 
been a familiar sight for ages before the marvel of it was 
recognised, the insect’s transformation of energy surpass- 
ing in its economy any human invention. But exactly 
when it was clearly understood that light may be a by- 
product of vital processes (or metabolism) it is hard to say. 
Till the beginning of the nineteenth century the 
luminescence of the sea, which we know to be due to a 
multitude of small organisms, such as Noctiluca, was a 
mystery, on a par with St. Elmo’s fire at the masthead (a 
slow brush-like discharge of electricity), or with Will-o’- 
the-Wisps moving over the swamps (probably due to the 
combustion of phosphine or of marsh-gas). 

In his monograph, The Nature of Animal Light, (1920), 
Dr. E. Newton Harvey, Professor of Physiology at 
Princeton, notes no fewer than thirty-six orders of animals 
in which luminescence is known to occur. And that is 
after excluding many alleged cases, for a “luminous” 
frog turns out to have dined well on fireflies, and everyone 
knows that the shining of the cat’s eyes in the dark is 
simply an interesting reflection. Although luminescence 


397 


308 SCIENCE, OLD AND NEW 


has been sometimes reported from animals living in 
fresh waters, e.g., in the larvee of a harlequin-fly, Professor 
Harvey will not admit that it occurs except on land or in 
the sea; and he also points out that there is no rhyme or 
reason in its distribution. It is seen in various Infusorians 
like Noctiluca, in numerous stinging animals like sea-pens 
and Portuguese Men-of-War, in the beautiful comb- 
bearers, in sundry worms and brittle-stars, in many crus- 
taceans and insects, in squids and a few other molluscs, 
in compound Ascidians like the Fire-flame (Pyrosoma), 
and in many fishes, especially from the Deep Sea. 


Cold Light 


More clearly than before Professor Newton Harvey puts 
animal light in its proper place. A body which gives off 
light-waves because of its high temperature is said to be 
incandescent, but when the light emission is stimulated 
by some other means than heat we speak of luminescence, 
and all animal light—‘‘cold light’’—1is of this nature. 
The emission of light by bodies after previous illumination 
or radiation is called phosphorescence, but animal light is 
not in this category. Nor is it fluorescence or electro- 
luminescence or crystalloluminescence—we dare not go on 
to bigger words still; animal light is due to the oxidation of 
some substance produced in the cells; it is a chemical or 
bio-chemical phenomenon. Its physical characters have 
been carefully studied in luminous beetles, such as “‘fire- 
flies,’ and the important general fact is that it is all 
visible light, with no infra-red or ultra-violet rays, and 
that it behaves like light from ordinary sources. ‘‘Like 
ordinary light, animal light will also cause fluorescence 
and phosphorescence of substances, affect a photographic 
plate, cause marked heliotropism of plant seedlings, and 
stimulate the formation of chlorophyll.” As Langley 
and Very pointed out in their well-known paper “‘On the 


LIVING LIGHTS 309 


Cheapest Form of Light” (1890), the luminescence of the 
firefly is all light and no heat. It is cheapest in the sense 
that none of the energy is lost in the form of heat. It is 
perfect “‘cold light’? and might be taken as an emblem 
of what scientific illumination ought to be. Moreover, 
Harvey agrees with Langley that there is no reason why 
man should not learn the method of the firefly for practi- 
cal purposes. 


The Production of Light by Organisms 


The light may be produced only 7” situ in the cells in 
which the photogenic substance is made, or there may be a 
luminous secretion which exudes over the surface of the 
body. This may form a glimmering trail in the sea or on 
the ground. The production of the light may be periodic, 
even rhythmic, or it may be continuous. It is interesting 
to find that some fishes, whose luminous organs are always 
active, are able to draw a blind over them, or to turn the 
lighting surface against the body-wall so as apparently to 
“turn off” the light. When the light comes from an 
extra-cellular secretion it is usually produced by relatively 
simple glands, diffusely scattered or definitely arranged. 
In cases where the seat of the light is intra-cellular, there 
are often elaborate luminous organs, well illustrated in 
various fishes, higher crustaceans and beetles, and Professor 
Harvey lays an interesting emphasis on the fact that these 
are often very like eyes. In front of the group of photo- 
genic cells there may be a lens, sometimes triple; behind 
them there may be a reflector; round the sides of the organ 
and behind the reflector there is often a dark envelope 
shutting off the light from the tissues of the animal itself; 
and then there is the nerve, stimulating or controlling. 
Now many an eye has its lens, its reflector, and its pig- 
mented envelope, so that there is often a very striking 
resemblance between an organ that produces light and one 


310 SCIENCE, OLD AND NEW 


that detects light. In the luminous organ, as Professor 
Harvey says, the important transformation of energy is 
chemi-photic; in the eye it is photo-chemical. But the nerve 
of the luminous organ is of the stimulating efferent order, 
while that of the eye is sensory and afferent. 


Luciferase and Luciferin 


Robert Boyle proved in 1667 that air is necessary for 
the luminescence of damp wood and dead fishes, and the 
not less ingenious Spallanzani showed in 1794 that while 
parts of luminous jellyfishes give forth no more light when 
they are dried, they will emit light as before when re- 
moistened. Boyle’s experiments practically proved that 
organic luminescence is of the nature of an oxidation; 
Spallanzani’s proved that it is not in the strict sense a vital 
process. These were first steps in the study of organic 
light, but there has been great advance since these early 
days. A very important result was reached by Raphael 
Dubois, a French zoologist, when he showed (about 1887) 
that a hot-water extract of the luminous tissue of the 
boring bivalve Pholas and a cold-water extract of the 
same, allowed to stand until the light disappears, will 
again produce light if mixed together. For this led 
Dubois to the theory that in the hot-water extract there is 
a substance, luciferin, not destroyed by heating, which 
oxidises with the production of light in the presence of 
a ferment or enzyme, luciferase, which is destroyed by 
heating. As Professor Harvey puts it: ‘‘The luciferase 
is present together with luciferin in the cold-water extract, 
but the luciferin is soon oxidised and luciferase alone 
remains. Mixing a solution of luciferin and luciferase 
always results in light production until the luciferin is 
again oxidised.” 

For a good-many years past Professor Newton Harvey 
has been following the clue which Dubois discovered, and 


LIVING LIGHTS 311 


in a monograph recently published, he states his conclu- 
sions and those of other investigators. As regards 
luminous beetles, the boring Pholas, and the small marine 
crustacean called Cypridina, it seems certain that the 
luminescence is due to the interaction of two very different 
substances, luciferin and luciferase, in the presence of 
water and oxygen. The luciferins and luciferases of 
different animals are different, but all luciferins have a 
good deal in common and similarly for luciferases. The 
chemical nature of luciferin cannot be stated at present, 
but it has much in common with stuffs like digested 
proteins (peptones). 

‘Luciferase is unquestionably a protein and all its 
properties agree with those of the albumins. Although 
used up in oxidising large quantities of luciferin, it behaves 
in many ways like an enzyme and may be so regarded.” 
It is calculated that one part of luciferase in 1,700 million 
parts of water will give light when luciferin is added, and a 
similar dilution of luciferin will give visible light when 
luciferase isadded. This certainly suggests that luciferase 
is an organic enzyme or catalyst which oxidises luciferin, or 
accelerates the velocity of oxidation of luciferin, with the 
result that light is produced. 


Uses of Luminescence 


When a living creature simply exudes a luminous secre- 
tion or sparkles as it burns up certain complex granules 
in various parts of its body, it is quite possible that the 
luminescence is not as such of any importance in the every- 
day life. It may be no more than the by-play of some 
physiologically important chemical change. No one feels 
bound to find a use for the luminescence of bacteria or of 
the eggs of fireflies. But the case is different when there 
is an elaborate luminous organ or a definite arrangement 
of organs. ‘The search for a use is then imperative. All 


312 SCIENCE, OLD AND NEW 


the suggestions that have been made remain more or less 
of a speculative character. (1) The light may serve to 
scare away intruders or to distract predacious molesters. 
(2) The light may be a lure attracting booty in the dark- 
ness of deep waters, and this seems plausible when the 
luminous organ is near the mouth. (3) The light may 
serve as a lantern, helping abyssal squids and fishes to find 
their way about. But this interpretation is applicable 
only when the hypothetical lantern is appropriately situ- 
ated, which it often is not. (4) The light may facilitate 
the recognition of kin, and serve as a sex-signal in mating. 
This fits in well with what is known of fireflies, and it is 
noteworthy that the toad-fish, Porichthys, is luminous 
only during the spawning season. It is evident that 
the chemical physiology of animal light has outrun the 
theory of its biological significance! It is probable that 
luminous organs have several different uses. The only 
certainty is that we must have more facts. 


XXXIX 





BACTERIA AND LUMINESCENCE 


313 


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pi a wh Wee, a ea i” 
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o hi Nears ah 


HAN Sh 


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* sng ik} i a 


wa ae 





BACTERIA AND LUMINESCENCE 


As we have seen in the preceding study, the physiology 
of luminescence (popularly and erroneously called phos- 
phorescence) has been carefully studied in the firefly, 
in a small crustacean called Cypridina, and in the rock- 
boring bivalve known as the piddock or Pholas. In these 
cases there appears to be an energetic interaction between 
a protein substance called luciferase and a somewhat 
peptone-like substance called luciferin which undergoes 
rapid oxidation. Just as an active muscle produces heat 
and electricity, so may another kind of tissue produce 
light. We do not propose to follow the general question 
further, but it is necessary to call attention to some recent 
work, some of which is rather upsetting. 


A Striking Case 


Not very long ago, Professor Newton Harvey studied 
two luminous fishes (Anomalops and Photoblepharon) 
common off the Banda Islands of the East Indian Archi- 
pelago. They have very large luminous organs, and they 
give out light without ceasing, by day as well as by 
night, and without requiring any provocation. This is 
unlike what occurs in other luminous fishes, where the 
light-producing material shines under the influence of 
certain stimuli, and is generally regarded as a secretion 
of glandular cells. 

315 


316 SCIENCE, OLD AND NEW 


In the Banda fishes the investigator could not demon- 
strate luciferin and luciferase, but under the microscope 
he found innumerable motile bacteria, and the suspi- 
cion arose in his mind that they were the cause of the 
light! For it is well known that there are various lumi- 
nescent bacteria, such as those which make dead fishes 
‘‘shine in the dark.” Professor Newton Harvey then 
found that, if the organ was dried and moistened again, 
it gave only a faint light, which is also true of luminous 
bacteria; whereas the luminous organs of most animals 
can be dried without much loss of their light-producing 
power when re-moistened. Again, the light was extin- 
guished without a preliminary flash by the addition of 
fresh water, which is likewise true of luminous bacteria. 
Poisons that put out the light of luminous bacteria had a 
similar effect on the light-organs of the fishes in question. 
So the suspicion grew into a hypothesis: that the light- 
organ of the Banda fishes is an incubator for the growth 
and nourishment of luminous bacteria living in partner- 
ship with the animal. 

Why, it may be asked, did not the investigator discover 
there and then whether the bacteria were the agents in 
producing the light? But he could not isolate them within 
the organ, and when he got them to grow by themselves 
in a jelly culture, they gave forth no light. This may mean 
that the hypothesis is wrong and that the light is produced 
by the living cells of the fish. Or it may mean that the 
bacteria will not light up except in certain surroundings 
and with certain food-supplies. It may be that they are 
not happy, so to speak, when the partnership is dissolved. 
Further experiments will answer this question. 


Borrowed Lights 


The case of the Banda fishes makes one ask whether 
there are many cases of luminescence due, or probably 


BACTERIA AND LUMINESCENCE 317 


due, to partner-bacteria, and much information on this 
subject has been recently made available by Professor 
Buchner in his great book on Symbiosis—that is to say, 
the living together of two kinds of creatures in mutu- 
ally beneficial internal partnership. The theory that the 
luminescence of an active animal might be due not to its 
own laboratories, but to the intense life of partner- 
bacteria, is not a new idea, but it has been usually regarded 
as having a very restricted application. Recently, 
however, numerous instances have been observed similar 
to that of the Banda fishes, which indicate more or less 
convincingly that luminescence is another pie in which 
bacteria have their finger. 

In two families of beetles, the fireflies and the Pyro- 
phores, there is brilliant luminescence, which often seems 
to be used in love-signalling between the sexes; and the 
generally accepted view has been that under nervous 
stimulation a ferment like luciferase produces or acceler- 
ates oxidation in a luciferin, with light as the result. In 
some cases the light-production is very definitely localised 
—for instance, in two eye-like lamps on the thorax of the 
large ‘‘Cucujo” of Tropical America. It is a remarkable 
fact that the eggs and grubs are luminescent as well as the 
adult; the torch is handed on from generation to genera- 
tion. But this is not unlike bacterial infection. The 
luminous organ may be reduced to powder and shaken 
up in water; what passes through filter-paper is still 
luminescent for a while. But this is again suggestive 
of bacteria, and so is the frequently observed continuation 
of the light after the death of the insect. The light is often 
unequal in the two sexes and at different times, which is 
against the bacterial theory; and yet we know in the case 
of diseases that the activity of bacteria may vary ac- 
cording to their vital “‘soil” and at different periods. 
Luminous bacteria give out light continuously, whereas 
the animal light seems often to be interrupted; but it is 


318 SCIENCE, OLD AND NEW 


possible that the apparent discontinuity is merely a 
contrast between very dim and very intense luminosity. 
Finally, in the cells of the insect’s luminous organ there are 
crowds of granulations believed to be photogenic, but 
the supporters of the new theory declare that these are 
the partner-bacteria. What is needed is a culture of the 
alleged partners away from their insect host, and evidence 
that light can be produced under these conditions. 


The Fire-Flame 


One of the most astonishing animals of the sea is the 
Fire-Flame, or Pyrosome, a tubular colony of pelagic 
Tunicates, brilliantly ‘‘phosphorescent’’ with greenish- 
blue light or with changing colours. The colony may be as 
long as one’s arm, and a big one will light up a dark room 
so that the furniture can be seen. A common size is the 
length of one’s hand. The wonderful light is discontinu- 
ous, and the lighting-up seems to require a stimulus, 
such as a touch or a splash from a wave. When the 
Fire-Flame is kept in an aquarium, it is brilliant for a 
time, and then the light fails. Both these facts seem 
to be against the bacterial theory of the luminescence. 
When a Fire-Flame is carefully examined, it is seen to be 
a tubular colony of thousands of individuals, and each 
individual has two luminous organs or spots like little 
jewels. In the cells of these small spots there are rod- 
like and horseshoe-shaped corpuscles of very minute 
size; and here the divergence of opinion again arises, for, 
while the old view regards the corpuscles as belonging to 
the Pyrosome itself, the new view interprets them as 
luminous partner-bacteria. 


Luminous Cuttlefishes 


The luminous organs of Fire-Flames are simple spots, 
but in many cuttlefishes they are very complex structures. 


BACTERIA AND LUMINESCENCE 319 


They may include a lens, a reflector, a dark envelope, and 
a central mass of light-producing cells. Inside these 
cells, according to Pierantoni, there are myriads of bac- 
teria, sometimes hunting in couples. Moreover, in many 
females there are ‘“‘nidamental”’ organs, usually regarded 
as having to do with the making of the egg-shells, and 
these, according to Pierantoni, are crowded with the 
bacteria. It almost looks as if they were organs for 
incubating the partner-bacteria. As to the presence of the 
bacteria there is no doubt; but the evidence that they 
produce the light does not appear to us to be convincing. 
And it is difficult, surely, to think out the evolution of an 
eye-like structure around a horde of tamed intruders. 

Professor Buchner is satisfied with the evidence that 
the luminescence of Fireflies, Fire-Flames, and Cuttle- 
fishes—three very diverse types—is due to luminous 
bacteria which have established a partnership or symbiosis 
with the animals. More than that, he thinks it is time 
to ask whether any multicellular animal produces its own 
light! Perhaps their luminescence is always a borrowed 
splendour after all! 

Personally we are not convinced that the evidence 
submitted justifies such a sweeping generalisation, es- 
pecially in cases where there is an elaborate eye-like 
luminous organ. But it is plainly a scientific duty to 
give the new theory careful consideration. 












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XL 


THE AGE OF THE EARTH 


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THE AGE OF THE EARTH 


AGAINST an early deductive view that a period of 6000 
years was about enough, we have a distinguished geolo- 
gist claiming that the more or less solid earth began 
861,000,000 years ago. He was often asked if he was sure 
as to the third figure in his estimate, but his answer was 
always the same, that the sum figured out in that way. 
The certainty is that the earth has an antiquity beyond 
our powers of conceiving and the most interesting question 
is how the scientific estimates have been arrived at, and 
why they should be so discrepant as they are. It may be 
mentioned at once that the discovery of radio-activity 
has affected the validity of all the previous limits which 
the leading physicists, like Lord Kelvin, had set to the 
demands of geologists and biologists. 


Lord Kelvin’s View 


The earth was supposed to be a self-cooling body; and 
investigators expert in such matters were able to argue 
back to the time when it ceased to be molten (if it was ever 
molten!). Arguing on these lines in 1862, Lord Kelvin 
estimated the age of the earth as a cooling body at some- 
thing unthinkable between 20,000,000 and 400,000,000 
years, with a probability of ninety-eight millions. But 
just as geologists began to be aware of the enormous 
thickness of second-hand or sedimentary rocks in the 


323 


324 SCIENCE, OLD AND NEW 


earth’s crust—perhaps over sixty perpendicular miles 
of them when all the quite different series are added up!— 
Lord Kelvin began to be less generous. He cut down 
the allowance in a cruel way when indulgent supplies were 
needed. It was about 1897 that he said:—‘We have 
now good reason for judging that the consolidation of the 
earth was more than twenty and less than forty million 
years ago; and probably much nearer twenty than forty.” 
From four hundred millions to forty millions was a bad 
drop—accompanied, too, by the threat that the allow- 
ance might have to be cut down to twenty millions! 
The biologists were ill at ease, for it takes a long time 
to make a system of animate Nature on Darwinian 
lines. They say it may have taken a million years to 
give the elephant his trunk, and there were many more 
important affairs than that. The fact is that Lord 
Kelvin was much influenced by some subtle inquiries into 
the tides and the moon—inquiries rather beyond the reach 
of most of us. How long had it taken to get the tides into 
the state in which they are now? Or how much time had 
elapsed since the moon was heaved off from the hot earth? 
There are ways of answering these questions. 

There seems to have been some unholy joy in certain 
camps when Lord Kelvin refused to allow the geologists 
and biologists all the time they asked for. But even 
a reduction to twenty millions was far from being an 
approximation to the 6000 years which those who 
‘wrested the Scriptures” held out for. The grand- 
children are now deciphering man’s records older than 
the grandparents would allow the earth to be. 


Radio-A ctivity 
In any case Lord Kelvin was wrong, for he was unaware 


of radio-activity. There is enough radium and uranium 
in the rocks of the earth’s crust to make the earth in some 


THE AGE OF THE EARTH 325 


measure a self-heating body; and this fact vitiates the 
calculations Lord Kelvin and his contemporaries made. 
As Lord Rayleigh said in 1921—‘‘ Radio-active methods of 
estimation indicate a moderate multiple of 1000 million 
years as the possible and probable duration of the earth’s 
crust as suitable for the habitation of living beings.” 
If this is sound, our geological friend was well within 
his rights in asking for 861,000,000! 

Some years ago Sir Ernest Rutherford inquired into 
the radium content of a uranium mineral found in Glas- 
tonbury granitic gneiss of the Early Cambrian. His 
question was how long it must have taken this radium 
content to form, and his answer was 500,000,000 years. 
And that liberal allowance of time was for the Early 
Cambrian alone! But we do not know whether this cal- 
culation holds to-day. These young sciences change 
rapidly. 


Other Estimates 


There are various ways of getting at the age of the earth 
from the geological side. As everyone knows, the surface 
of the earth weathers away; the mountains are always 
flowing into the sea. There are delivered into the sea 
every year from the United States alone 783,000,000 tons 
of rock materials. The average rate of denudation for 
North America is a foot in 8600 years. The solid particles 
and fragments that result from erosion go to form sedi- 
ments, and the dissolved matter may be captured by ani- 
mals whose shells also go to form sediments. Thus in the 
past there have been formed the sedimentary rocks, e.g., the 
sandstones, mudstones, and limestones that form a large 
part of the earth’s crust. Now if all the thicker beds of 
sandstones, mudstones, and limestones that have been 
formed at different times be pieced together in vertical 
sequence, they make a pile fifty-three miles in thickness 


326 SCIENCE, OLD AND NEW 


as a mean estimate, with a maximum thickness of about 
ten miles more. It is evident that the time required to 
erode the ancient rocks and remake them as sedimentary 
rocks must be prodigious. The calculation makes the 
assumption that lies at the roots of uniformitarian 
geology, that the rates of erosion and deposition have not 
been in the past very much greater than they are today. 
This assumption obviously suggests caution and the 
desirability of confirmatory evidence. 


The Saltness of the Sea 


So we turn to another method which takes us back to 
the time of the ingenious Edmond Halley, who was the 
first astronomer to predict the return of a comet. About 
1715 Halley suggested that the earth’s age might be com- 
puted from the amount of common salt in the sea. For 
all the sodium chloride in the sea is the outcome of sodium 
filched from the rocks by rain and rivers, and brought to 
join its equivalent of chlorine in the sea. It is calculated 
that the sea receives every year 63,000,000 tons of sodium 
in solution. The primordial sea-water was relatively 
fresh, and it is possible to calculate from its annual in- 
come how long the sea has taken to become as rich in 
salt as it is to-day. The answers given have, as usual, 
varied considerably; thus Professor Joly estimated 90-100 
million years, and Professor Sollas 80-150 millions. Al- 
lowing something for a greater supply of sodium in early 
days, when the bulk of the earth’s surface was covered with 
granitic and igneous rocks, we may take 100,000,000 as an 
average of the computations by various investigators. 


General Result 


The present-day position has been recently stated by a 
distinguished American geologist, Professor Schuchert. 


THE AGE OF THE EARTH 327 


Since the discovery of radium all the calculations previously 
made, have been set aside by the new school of physicists, and 
now geologists are told they can have 1,000,000,000 or more 
years as the time since the earth attained its present diameter. 
. . . Even if finally it shall turn out that the physicists have 
to reduce their estimates as to the age of certain minerals and 
rocks, geologists nevertheless appear to be on safer ground in 
accepting their estimates than those based either on sedi- 
mentation, chemical denudation, or loss of heat by the earth. 


We have touched but lightly on a very difficult sub- 
ject, in regard to which anything like dogmatism would be 
foolishness. Yet the general result of increased knowledge 
has been to show that the drafts which geologists and biol- 
ogists draw on the bank of time are likely to be honoured. 
We have said almost nothing about the length of time 
required for organic evolution, for the data as to the rate 
of evolution are very precarious. We know from the rock 
record when certain types—say the Flying Dragons— 
appeared and when their dynasty came to an end. The 
geologists can give us some indication of the fraction of 
the total duration that must be granted to a given epoch. 
If, then, we accept a total like the 861,000,000 years 
already referred to, we can tell approximately when the 
Pterodactyls began and when they ceased tobe. But the 
less we say about the rate of organic evolution the clearer 
will be our intellectual consciences. 








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XLI 


HOW THE ELEPHANT GOT ITS TRUNK 


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HOW THE ELEPHANT GOT ITS TRUNK 


ONE of the disappointments which the impatient 
evolutionist soon meets with is the lack of data in regard 
to the pedigree of many of the most interesting types. 
The origin of birds, for instance, remains obscure, except 
that we are reasonably certain that they sprang from 
a stock of extinct reptiles, a sub-order of the Dinosaurs. 
Or, again, the origin of backboned animals is a problem 
still unsolved; its discussion is hardly beyond the specula- 
tive stage. On the other hand, there are some cases 
where the lineage has been well registered in get-at-able 
fossil-bearing rocks, so that the story has been clearly 
read. One of these cases is the elephant. 


Modern Elephants a Climax 


Every age has its giants, and those of to-day are the 
whales, the giraffe, and the elephants. The African 
elephant, according to Sir Samuel Baker, reaches a height 
of 12 feet; and we know that the once-famous Jumbo 
stood 11 feet high at the shoulder and weighed 6% tons. An 
average pair of tusks may weigh 75 pounds and 65 pounds, 
left and right respectively, and Sir Samuel Baker reports 
one that had the prodigious weight of 188 pounds! Yet in 
spite of its gigantic size the elephant can keep up a speed 
of ten miles an hour for a long distance. The Indian 
elephant is not quite so huge as the African species, but is 


331 


332 SCIENCE, OLD AND NEW 


nevertheless a Colossus. So was the woolly mammoth of 
the Siberian forests—a Goliath whose David was primitive 
man. He not only killed him; he drew him on the walls 
of the caves. There was once an African species bigger 
still, standing about 13 feet high. We are not forgetting 
the dwarf or ‘‘pony”’ elephants whose remains are found 
in Malta, but our point is the obvious one that the true 
elephants of the genus Elephas are mostly giants. How, 
then, and where did the race of giants begin? 


Pioneers 


Millions of years ago, in the Eocene epoch, when there 
was a warm and moist climate and luxuriant vegetation 
in many parts of the world, when grassy plains were 
established in many places, there lived in North Africa 
a primitive hoofed animal called Moeritherium. It was 
about the size of a tapir or of asmall donkey. Unless the 
skull is very deceptive, this ancestor of the elephants, for 
such it is, had, like the tapir, a short snout, useful for 
gripping the herbage. An elephant’s trunk is a pro- 
longation of the nose and the upper lip, and there is an 
indication of it in various mammals. Thus it crops up 
in the desman of the Pyrenees, an aquatic relative of the 
mole, which used to be represented in Britain. In this 
creature the flexible proboscis is used in catching small 
water animals, and it is said to be capable of being curved 
round so as to push food into the mouth—which the ele- 
phant does with its trunk. This is Nature’s way, to take 
a very old thing—in this case the upper lip and the nose— 
and make out of it a very new thing—namely, a flexible 
trunk. 

But we are wandering away from the Moeritherium, 
whose remains are found in considerable quantities in the 
region known as the Fayum, in Lower Egypt. Apart 
from the large nasal opening in a somewhat backward 


HOW THE ELEPHANT GOT ITS TRUNK 333 


situation (indicative of a proboscis), the primitive crea- 
ture had the second incisors on the upper and lower jaw 
enlarged into tusks, the grinding teeth were transversely 
ridged, and the bones of the back of the skull were begin- 
ning to be lightened by air-cells. 


Progress in the Proboscis 


Ages passed, and alongside of Moeritherium there 
emerged in the Lower Oligocene a larger creature called 
Palzomastodon. It stood from 4-6 feet high, according 
to the species. The snout had lengthened, the nose- 
opening was further back, the canine teeth had disap- 
peared, and likewise the front teeth, except two pairs of 
tusks; there were more ridges (namely, three) on the big 
grinding molars, and there were more air-cells at the back 
of the skull. In short, the Palaomastodon was much 
nearer the elephant. It was also an Egyptian mammal, 
and it was kept from spreading to the north by a broad 
and deep sea which united the Atlantic to the Pacific. 
There is a gap in the rock-record through the Upper 
Oligocene, but in the Miocene there appeared the trium- 
phant Tetrabelodon, as large as a medium-sized elephant. 
Its remains occur in Europe, Asia, and North America, 
as well as in Africa, so the great sea previously referred 
to must have been, in part at least, replaced by land. 
In Tetrabelodon the nostrils are still further back, the 
upper tusks have grown stronger, the grinding teeth have 
more ridges, the skull has more air-cells. It is probable 
that there was still a stiffish snout, supported by the 
elongated front of the lower jaw, but according to the 
leading British authority, Dr. Charles W. Andrews, in 
his masterly British Museum Guide to the Elephants (a 
scientific romance costing one shilling): ‘“‘the end of the 
upper lip and nose was probably free and movable, and 
may even have been able to grasp objects to some extent.”’ 


334 SCIENCE, OLD AND NEW 


While the race of elephants was increasing in size, the neck 
was getting shorter; for such a big head could not be borne 
on a long neck. It follows that if the animals were to 
continue to be able to reach the ground the snout would 
have to become longer. It is very interesting to find 
in the earlier species of Tetrabelodon a long lower jaw 
with tusks suited for grubbing in the earth, while in the 
later species the lower jaw ‘‘was shortening up and could 
no longer reach the ground, but doubtless the fleshy 
upper lip and nose, now freed from their bony support for 
at least part of their length, became flexible and better 
adapted for grasping the animal’s food.” This is how 
the elephant got its trunk, pace Mr. Kipling. 


The Modern Elephant 


Ages passed, and in the Pliocene epoch there appeared 
the elephants proper, in some ways linked back to Tetra- 
belodon by the Mastodons. The shortening of the chin con- 
tinued and the lower tusks fell away; the back teeth became 
more complicated, with an increasing number of transverse 
ridges; the upper tusks grew stronger and the trunk grew 
longer. To support the great tusks and the grindstone- 
like molars meant an enormous skull, which was also of 
service to afford insertion-surface for the strong muscles of 
the trunk—able to lift a tree. But the increased develop- 
ment of huge air-cavities in the skull-bones counteracted 
the tendency to an over-increase of weight. Improve- 
ments went on hand in hand—in correlation. 

The elephant is a big bundle of fitnesses, and we must 
not forget the remarkable straightness of its imbs—that 
is to say, the absence of angles at the joints. This is also 
seen in some extinct mammals of gigantic size, such as 
Titanotherium, which do not belong to the elephant 
alliance. But Professor H. F. Osborn is probably right 
in interpreting the vertical pillars not as primitive features 


HOW THE ELEPHANT GOT ITS TRUNK 335 


but as secondary adaptations to support the huge bulk. 
Another interesting characteristic of the elephant’s 
limbs is the way they end. There are five digits on both 
fore and hind feet, but these are embedded in a huge 
cylindrical mass of flesh and skin, so that only the tips 
of the hoofs are seen on the under surface. 


General Reflections 


Evolution is a formula for the way in which living 
creatures have come to be as they are—new kinds arising 
out of old kinds and often ousting them. It is not the 
sort of conclusion that can be proved, as one can prove 
the conservation of energy in an experiment or the change 
of uranium into radium. But it is the only conclusion 
open to us, and it is a key that fits. Obscurantists who 
call for proofs should study the patient work of paleon- 
tologists, like Dr. Andrews, who have worked out the 
pedigree of the elephant. It is as convincing as the pedi- 
gree of the horse. 

One cannot but be impressed by the bigness of the 
change from the little Moeritherium of the Eocene marshes 
to the giant elephants in the jungle, and yet, from another 
point of view, one is impressed by the leisureliness of the 
process. They say it must have taken about two million 
years to get rid of the lower tusks. Of course, elephants 
are long-lived, slow-breeding animals. 

In the story of the elephant we got glimpses of the plus 
and minus method of evolution. The process of trans- 
formation works by adding on—more and more folds on 
the massive molars, longer and longer tusks, stronger and 
stronger musculature in the trunk, more and more con- 
volutions in the cortex of the fore brain. But it also 
works by cutting off—shortening the lower jaw, getting 
rid of the lower tusks and the canines, reducing the 
number of back teeth; and the striking thing is that 


336 SCIENCE, OLD AND NEW 


parallel changes of adding on and lopping off seem to 
have taken place independently in widely separated 
parts of the world. This shows that they are under 
‘the reign of law.” 

Another glimpse of Nature’s methods we have already 
alluded to—the making of the new out of the old. The 
ereat tusks, what are they but overgrown incisor teeth? 
The extraordinary ridges of the molars, what are they 
but exaggerated plaitings of the enamel into the ivory? 
The mobile proboscis, able to lift a needle or a log, a penny 
or a pail, what is it but an extraordinarily long nose, with 
something due to upper lip? The nostrils run the entire 
length, and the tip bears a delicate finger-like process in 
the Indian elephant, two of them in the African species. 

But it may be said that all this does not tell us how 
the elephant got its trunk, but only the stages in the pro- 
cess of acquisition. The honest answer is that we cannot 
go much further at present. The germ cells are fountains 
of change—something new is always welling forth. 
We can suggest reasons why this should be so, but that 
is another story. What is certain is the continual crop 
of novelties arising from within, but determined in some 
measure by what has gone before, and in some measure 
by the nature of the material. But given the novelties— 
often outcropping in correlated groups—and given the 
sieves supplied by the struggle for existence within the 
system and economy of animate nature, perhaps we need 
no more to understand how the elephant got its trunk. 


XLII 


THE ORIGIN OF LAND PLANTS 


337 








THE ORIGIN OF LAND PLANTS 


THE more one thinks about the conquest of the dry 
land by adventurous animals of aquatic ancestry, the more 
convinced one becomes of the impossibility of success if 
plants had not led the way. Plants ensured the food, the 
moisture, the shelter without which the dry land would 
have been altogether too inhospitable for animals. Thus 
the problem of the origin of land plants has an enhanced 
interest. 


Marine Plants First 


It seems quite certain that many ages passed before 
there were any land plants at all. In Cambrian, Ordo- 
vician, and Silurian strata there are plenty of traces of 
seaweeds, but there are no known fossil land-plants, before 
the Devonian. Among the earliest are the very inter- 
esting Devonian fossils discovered a few years ago at 
Rhynie in Aberdeenshire by Dr. Mackie of Elgin. Of 
course it is quite possible that there may have been pioneer 
land plants long before the Devonian, but of a type too 
simple to admit of definite fossilisation. 


The Colonising of the Land 


If there is any orthodox view or majority report in 
regard to the origin of terrestrial plants, we suppose it 


339 


340 SCIENCE, OLD AND NEW 


would be something like this: the simplest plants began 
in the sea and flourished there for ages, but some of them, 
obedient to the universal impulse to explore empty corners, 
made their way from shore to estuary, from estuary to 
river, from river to lake, from lake to swamp and marsh, 
and thence, at last, began to colonise the dry land. At 
each station in their ascent some would no doubt settle 
down and specialise as best they could in relation to the 
immediate environment, while others would push on, 
trying as it were to find something better. Whether some 
may not have passed directly from the sea-shore to the 
shore-marsh and thus on to dry land, without serving an 
apprenticeship in the fresh-waters, is a question in detail 
which many be waived for the present. But the general 
idea of the theory sketched is that relatively simple 
plants, endowed with considerable travelling power, like 
many of the unicellular algee, did the exploring, and that 
structural evolution began afresh, as it were, in the suc- 
cessive stations where they established themselves. One 
must remember that detached propagative parts of plants 
would not readily migrate up-stream, though spores 
might be borne by the wind. Fishes may have helped 
in transport, but there were no plant-distributing birds 
in those early days. Moreover, there were no true seeds 
before the Devonian. The general idea seems to be that 
very simple plants did the travelling, and that when 
they reached a suitable resting-place they proceeded to 
evolve into organisms like our liverworts, mosses, and 
ferns, building up structural complexities somewhat 
similar to those that had already been achieved among sea- 
weeds in salt water, similar yet different, being adapted 
to the quite novel conditions of terrestrial life. In his 
masterly book, The Origin of a Land Flora (1908), Pro- 
fessor F. O. Bower has sought to show how the exaggera- 
tion of the spore-bearing (sporophyte) generation and 
the suppression of the sex-cell-bearing (gametophyte) 


THE ORIGIN OF LAND PLANTS 341 


generation, a change characteristic of all flowering plants, 
would follow as a natural outcome of plants establishing 
themselves in a terrestrial habitat. But the prior question 
is how the transition from aquatic to terrestrial (or sub- 
aérial) conditions may have been effected. 


A New Theory 


To this question a new answer has been recently given 
by the distinguished Oxford botanist, Dr. A. H. Church, 
in an essay entitled Thalassiophyia and the Subaérial 
Transmigration (1919), an essay as full of suggestive 
ideas as it is of repellent terms. We seldom came across 
a book so gratuitously discouraging to the reader, and 
yet such good sport from cover to cover. Dr. Church’s 
general idea is that terrestrial plants arose by the gradual 
transformation of highly-evolved marine plants on a 
slowly rising beach. ‘Transmigration seems to mean 
‘“‘transition im situ.’ ‘‘When the first land gradually 
lifted above the primal sea, bearing all forms of marine 
life on it, the successful transmigrant alge of the first 
land-migration combined the best and highest factors of 
marine equipment.’”’ What had been gained in the sea 
in the course of ages was not lost, to be invented de 
novo a second time, it was adapted. It was not in the 
reproductive part of the plant that the profoundest 
changes were necessary, it was the body that required 
to be readjusted from life in an aqueous food-solution 
to life in an atmospheric medium with no external food- 
solution beyond the soil-water bathing the roots. 


Three Epochs in Plant History 
After the gradual cooling of the earth there were, 


according to Dr. Church’s picture, three great epochs of 
world-construction, with associated vegetations. There 


342 SCIENCE, OLD AND NEW 


was the time of the condensation of water-vapour to form 
the sea, which he supposes to have covered the earth, 
and the surface-waters of that sea were peopled by 
microscopic plants sufficient unto themselves. This 
was the Plankton Epoch. Second, the folding of the earth’s 
crust raised parts of the floor of the sea within the reach 
of light, and minute plants began to settle there, anchor- 
ing themselves and proceeding to build up fronds and other 
forms of body. But anchoring on a substratum made it 
necessary to have some new arrangements to secure dis- 
persal—a return to the plankton phase for processes of 
reproduction, much in the same way as we see in sponges 
which liberate free-swimming embryos, or in zoophytes 
which liberate swimming-bells or medusoids. A new note 
was struck: the types that survived were those whose 
individual members had moved in the direction of race- 
continuance—the most fundamental of all biological 
truisms. To the plankton-law of self-preservation was 
added the benthos-law of race-continuance. ‘‘The fact 
that any race still exists implies that the individuals 
collectively have done their bit.” This was the Benthos 
Epoch. Third, there was the gradual emergence of dry land 
and the gradual transformation of aquatic vegetation— 
seaweeds in short—into a land-flora, able to absorb 
gases from the air and salts in solution from the sub- 
stratum. The Benthos introduced the new factor of sub- 
stratum, but the emergence of the land introduced the 
new factor of atmosphere. This was the Xerophyte Epoch. 
In other words, we must think: (1) of the primal Open 
Sea, with its free-swimming minute green plants; (2) of 
the floor of the illumined shallow sea with its anchored 
fronds all intent on experiments in body-making on the 
one hand and in reproductive dispersal on the other; 
and (3) of the beach slowly rising, foot by foot, millennium 
after millennium, with its highly evolved seaweeds 
slowly transforming themselves into land-plants. 


THE ORIGIN OF LAND PLANTS 343 


Sieves in Evolution 


The energy of growth, at bottom a phase of chemical (ionic) 
activities, supplies the driving-power of life, and such “‘life’”’ 
beats against the sieve of Natural Selection; but this alone 
does not account for all the manifestations of plant-organisa- 
tion. Twice in the history of the world the sieve itself has 
been changed: the ‘‘ hidden hand’”’ which did this, and so de- 
termined the path to be taken as a sequence of progression, 
was not “‘ Nature” or ‘‘ Divine Guidance,” except in so far as 
such expressions may be utilised to cover an inevitable march 
of events, but in this case merely the expression of the cool- 
ing of the earth, which (1) lifted the sea-bottom by tectonic 
changes, and (2) ultimately lifted the ‘“‘land’”’ above the sur- 
face of the water, to be subjected to subaérial denudation to 
form ‘‘soil.”’ 


Of course, only a few of the plankton creatures got 
through the sieve to become anchored seaweeds on the 
subtratum, and only a few of the benthic plants got 
through the new sieve to become the pioneers of a land 
flora. The idea of an evolution of sieves as well as an 
evolution of the sifted material is useful, but we should 
not be inclined to restrict the operations of the ‘‘hidden 
hand”’ to twice. 


Transformation of the Seaweeds 


It is very impressive to visit a rocky foreshore at the 
lowest tide, to wade out among the Laminarians and other 
seaweeds not usually exposed at all, to observe the vigour 
and manifoldness of their growth and the complexities 
of their structure, and to realise that one is moving amid 
an antique vegetation, some members of which may be 
much older than the hills. The conventional view is that 
these seaweeds represent a gorgeous blind alley, but Dr. 
Church asks us to consider the possibility that from among 


344 SCIENCE, OLD AND NEW 


such highly evolved creatures the land flora may have 
emerged by gradual transformation as the foreshore slowly 
rose. The transformation cannot be thought of in any 
easygoing way. It meant that the seaweeds’ gripping 
structures, mere holdfasts, not true roots at all, became 
provided with rootlets and root-hairs suited for the absorp- 
tion of water and dissolved salts from the soil. It meant 
that a frond-surface, adapted for the absorption of watery 
food-solution, became fit for the absorption of the dry 
gases of the air. It meant the elaboration of a complicated 
vascular system for conveying the raw materials and the 
elaborated materials from part to part. Theseare the more 
readily stated difficulties which are faced and ingeniously 
countered by Dr. Church. 

Many a plant is a very plastic or modifiable creature, 
and even such a stable structure as a tree can adapt itself 
almost out of recognition to unusual conditions of life. It 
may be that individually acquired modifications ham- 
mered on each successive generation of seaweeds on the 
rising shore, but never taking hereditary grip (for that 
would be Lamarckism!), served as life-saving screens until 
germinal variations in the same direction had time to 
establish themselves as appropriate somatic adaptations. 

The migration theory of the origin of land-plants, with 
which we started, is not an easy theory. Fresh-water 
alge are rather of the nature of “‘depauperated relics.” 
‘‘To pass from the sea to fresh water implies starvation 
and deterioration of the output of reproductive cells, and 
hence failure to compensate the wastage of the race, and 
extinction.”” Perhaps this smacks a little of ex parte 
judgment, but there is the further difficulty of thinking 
of simple migrants from pond and swamp beginning 
de novo the elaboration of structural equipments which 
many of the seaweeds had already achieved. In place 
of this theory Dr. Church offers us ‘‘the epic of the 
stupendous epoch of a world-transmigration.” 


THE ORIGIN OF LAND PLANTS 345 


The cells and somatic organisation of all land-plants, as 
also all their reproductive cycles and mechanism, are but the 
continuation of the mechanisms evolved in the sea, to suit the 
conditions of life in the sea, as the best response possible under 
such conditions; and though the mechanism may be emended, 
modified or superseded in innumerable details, the primary 
plan of the architecture and the entire range of general prin- 
ciples of organisation remain essentially marine. 


Such a view certainly deserves careful consideration. 
It is in general idea in harmony with what we learn so 
often in the study of animal evolution, that apparent 
novelties are only very old structures transformed. 
New lamps out of old has been one of the great methods 
of evolution. And as to the maternal sea, why, its tides 
still echo in the chemical composition of our blood! 


8 
i ; 


i 





Dob 


THE ROMANCE OF THE WHEAT 


347 





THE ROMANCE OF THE WHEAT 


WE remember seeing half a century ago in the Low- 
lands of Scotland the carting home of the Maiden, the 
last sheaf from the last outstanding field of corn. It was 
part of the Kirn festival, the English harvest home, and, 
we suppose, the decorated sheaf stood for Ceres, as the 
word cereal suggests. We did not understand then how 
much there was to be grateful for—that the sheaf of 
wheat was the consummate instance of man’s co-operation 
with Nature. For, within the limits of the ponderable, 
was not the discovery, and cultivation of the wheat the 
most far-reaching of all man’s doings? Even in relation 
to the life that ‘‘means more than food,’ we cannot go 
far without our daily bread, and for a large fraction of our 
race that is made of wheat. Where did wheat come from? 
What is the science of Demeter’s gift? 

‘History celebrates the battlefields whereon we meet 
our death, but scorns to speak of the ploughed fields 
whereby we thrive; it knows the names of the king’s 
bastards, but cannot tell us the origin of wheat. That is 
the way of human folly.”” These two sentences from J. 
Henri Fabre, obviously written long before Mr. H. G. 
Wells’ Outline of History, are set in the forefront of one 
of the most fascinating of recent books, Professor A. H. 
Reginald Buller’s Essays on Wheat (1919). We wish to 
select from this scientific romance some pictures that give 
us a glimpse of the history of the most useful plant in the 
world. 


349 


350 SCIENCE, OLD AND NEW 


Pre-historic Wheat 


It is well known that Neolithic man grew wheat, and 
some have put the date of the first harvest at between 
fifteen thousand and ten thousand years ago. The ancient 
civilisations of Babylonia, Egypt, Crete, Greece and 
Rome were largely based on wheat, and it is highly prob- 
able that the first great wheat fields were in the fertile 
land between the Tigris and the Euphrates. The oldest 
Egyptian tombs with wheat, which never germinates after 
its long rest, belong to the first dynasty and are about 
six thousand years old. But there must have been a 
long history before that. 


The Wild Wheat of Hermon 


Now, while everyone knows something about wild oats, 
and a few know a little about wild barley and wild 
rye, it was not till the beginning of this century that wild 
wheat was discovered. It grows on the slopes of Mount 
Hermon. It is true that a botanist called Kotschy had 
collected it and pressed it in 1855 and that Kéornicke 
had named it in the herbarium at Vienna in 1873, but 
it was not till 1905 that Aaron Aaronsohn, Director of the 
Jewish Agricultural Experiment Station at Haifa, in 
Palestine, following the hint from Germany, had the good 
fortune to find the living plant growing in considerable 
abundance and exhibiting notable variability. ‘“‘It 
grows only upon the slopes of the most arid and rocky 
hills, and in places exposed to the hottest rays of the 
Oriental sun.’ The idea that Triticum hermonis is an 
escape cannot be entertained for a moment; it behaves 
in every way as a truly indigenous plant. 

It cannot be circumstantially proved that the wild 
wheat of Palestine is the veritable ancestor of all the culti- 


THE ROMANCE OF THE WHEAT 351 


vated wheats (always excepting the einkorn, which stands 
by itself and does not produce fertile hybrids when 
crossed with other kinds), but it is certain that if another 
ancestor is found it will be very like the Hermon species. 
One of the primitive features is the possession of a fragile 
rachis (the axis bearing the spikelets), which breaks 
readily into segments so that the seeds fall apart and are 
scattered. This character, well seen in the wild wheat 
of Hermon and in wild grasses related thereto, persists in 
inferior cultivated wheats like emmer, spelt and einkorn; 
in the others it has been replaced by a rigid rachis which 
is very much better for thrashing, though a hindrance 
in natural dissemination. According to Aaronsohn, there 
is strong evidence for regarding the Hermon wheat as 
the ancestor of emmer, which was cultivated in the Neo- 
lithic Age, and emmer as the ancestor of all the ordinary 
wheats. So we must think of Neolithic man noticing the 
big seeds of the Hermon wheat, gathering some heads, 
breaking the brittle rachis in his hands, knocking off the 
rough awns or beard, bruising the spikelets till the glumes 
or chaff separated off and could be blown away, chewing 
a mouthful of the seeds—and determining to sow and sow 
again. 

One of the interesting peculiarities of the wild wheat of 
Palestine is that it is well adapted for cross-pollination 
by the wind, though self-fertilisation also occurs. The 
interest of this observation is twofold: (1) that most 
grasses have flowers adapted for cross-pollination, so that 
in this respect the wild wheat is like the majority of its 
kind; but (2) that most cultivated wheats show self- 
pollination, though the other method tends to occur 
in warm countries. According to Professor Buller, “‘we 
may therefore regard our cultivated wheats as sexually 
degenerate. Since the wild wheat of Palestine has cross- 
fertilised flowers, there seems good reason for supposing 
that in our cultivated wheats self-pollination came to 


352 SCIENCE, OLD AND NEW 


replace cross-pollination under conditions of domestica- 
tion.”’ What usually happens in our wheats is this: at 
the flowering time, when the temperature is suitable, the 
glumes diverge rapidly and suddenly, often in the early 
morning; the filaments of the stamens grow quickly, 
the anthers project, open, and empty about a third of their 
pollen on the stigma of the same flower, the rest being 
scattered in the air. This takes about a minute, and after 
a quarter of an hour the glumes automatically close again. 
The first flowers to open are about the middle of the ear, 
and the process spreads gradually upwards and down- 
wards for the space of four days. Fertilisation has been 
effected. 


Variability of the Wild Wheat 


The wild wheat of Hermon is a virile plant, able to look 
after itself. It is marked by grass-like habits, relatively 
short straw, drooping long-bearded heads, the brittle 
floral axis already referred to, and big seeds such as would 
catch the eye of an observant and hungry Neolithic man. 
But it shows another interesting quality, namely, varia- 
bility; for Mr. Aaronsohn found a considerable number of 
different forms. ‘The interest of that is obvious, for it 
has doubtless been by taking advantage of the variations 
that have cropped up in the course of many millennia 
that man has been able to establish one successful race 
after another on his fields. For thousands of years, how- 
ever, the cultivation must have been very haphazard. 
Many varieties grew together in the field, though not 
mixing very much after self-pollination was established, 
and the husbandman chose a mingled lot of good ears to 
furnish seed for the next sowing. Virgil refers in the 
Georgics to the gathering of the largest and fullest ears in 
order to prevent degeneration. This was selection, but it 
was somewhat rough and ready. 


THE ROMANCE OF THE WHEAT 353 


The Emergence of Modern Wheat 


In the first quarter of the nineteenth century, however, 
a great step was taken, namely, the beginning of the de- 
liberate selection of individual ears and a segregation 
of the progeny. According to Professor De Vries, the 
first to recognise that the wheat-field contained a medley 
of different varieties was Lagasca, a Spanish Professor of 
botany, who gave the hint to Colonel Le Couteur in 
Jersey, with the result that a number of varieties were 
sifted apart, and a particularly good one, ‘‘Talavera de 
Bellevue,’ was placed on the market. About the same 
time the method of isolation and segregate-cultivation 
was taken up by Patrick Sheriff, of Haddington in Scot- 
land, whose achievements are inestimable. Another 
contributor was Vilmorin, who introduced what he called 
the ‘“‘amelioration of the race,” or the continued singling 
out of the best representatives of a pure strain. The 
isolating of individual promising variations and making 
each the beginning of a pure line has been the prevalent 
method of recent years, and has led to remarkable re- 
sults in the hands of investigators like Nilsson-Ehle in 
Sweden and Hays in Minnesota. 


The Story of Marquis Wheat 


But the modern method will become clearer if we take 
the particular case dealt with in most detail by Pro- 
fessor Buller—the famous Marquis Wheat, which was of 
so much importance in assisting the Allies to overcome the 
food crisis in the darkest period of the war. In 1917 
upwards of 250,000,000 bushels of this variety were raised 
in North America, and in 1918 upwards of 300,000,000 
bushels; yet the whole originated from a single grain 
planted in an experimental plot at Ottawa by Dr. Charles 
E. Saunders so recently as the spring of 1903. Marquis 


354 SCIENCE, OLD AND NEW 


is a hard, red, spring wheat with excellent milling and 
baking qualities; it is now the dominant spring wheat in 
Canada and the United States; it is very prolific and ripens 
early; it has enormously increased the wealth of the world 
in the last ten years. 

Now, the point is that Marquis was discovered deliber- 
ately in the course of precise searching for a variety 0° 
wheat well suited for Western Canada. Its parent on the 
male side was the mid-European Red Fife, a valuable 
variety with a very interesting history; its parent on the 
female side was rather a nondescript, not pure-bred, 
called Hard Red Calcutta that was imported from India 
into Canada some thirty years ago. It had the good 
quality of early ripening, but linked with this were unde- 
sirable qualities such as poor yield, very short straw, 
and the scattering of the grains from their glumes when 
ripe. So the inheritance from the maternal side was not 
brilliant. The father seems to have been the source of 
most of Marquis’s virtues, for Red Fife was, and still is, 
a first-class cereal which first ‘‘established the reputation 
of the Dominion for the production of high-grade wheat 
with excellent milling and baking qualities.” 


One of its kernels was conveyed in a cargo of winter wheat, 
via the Baltic and the North Sea, from Danzig to Glasgow; a 
sample of the cargo containing the kernel in question was pro- 
cured by someone at the Scottish port; this sample was sent 
to David Fife at his farm in Ontario about the year 1842; 
this single kernel germinated and produced a plant with three 
heads; the kernels of these three heads, when sown the next 
year, gave rise to the wheat which became known as Red 
Fife. 


So much for the parents of Marquis; but how was Mar- 
quis discovered? The result of the cross was a mixture 
of types, nearly a hundred varieties altogether (besides 
strains within the varieties), and it was by the system- 


THE ROMANCE OF THE WHEAT 355 


atic testing of these that Dr. Saunders hit upon Marquis. 
He worked steadily through the material, “‘studying 
head after head, and selecting out as many different and 
promising ones as he could find.’”’ Each head selected 
was propagated, most of the results were rejected, but 
finally Marquis emerged, rich in constructive possibilities, 
probably the most valuable food-plant in the world. ‘‘The 
first crop of the wheat that was destined within a dozen 
years to overtax the mightiest elevators in the land was 
stored away in the winter of 1904-1905 in a paper packet 
no larger than an envelope.”’ Well may we speak of the 
romance of the wheat. 


XLIV 


TOWARDS SOCIALITY 


357 





TOWARDS SOCIALITY 


IT is interesting to try to discover what one may call 
the main trends of organic evolution—lines of movement 
in a definite direction exhibited independently by unre- 
lated groups. ‘Thus in different phyla there is a very 
obvious trend in the direction of improving the nervous 
system, another in substituting sexual for asexual repro- 
duction, another towards viviparity, another towards the 
conquest of the dry land, andsoon. Has not one of these 
big trends been in the direction of sociality—the combina- 
tion or association of kindred creatures in various ap- 
proaches to corporate unity? 


A geregates and Integrates 


In the course of evolution there have certainly been 
many important aggregations and integrations in Nature. 
Corpuscles formed atoms, and atoms molecules, and 
molecules groups of molecules, and groups of molecules 
may have integrated into living matter. Ages passed, 
and there were finely finished minute organisms, the early 
Protozoa and Protophyta, most of which remained, 
however, in a non-cellular phase of being. Ages passed, 
and from among these non-cellular (or unicellular) crea- 
tures there was a gradual emergence of organisms with 
many-celled bodies, and of the origin of these we get some 
hints from certain Protozoa and Protophyta of to-day, 


359 


360 SCIENCE, OLD AND NEW 


which are in the habit of forming loose colonies with little 
or no division of labour. Alongside of these inorganic 
and organic aggregations and integrations there have been 
of course, processes of an opposite tendency. There have 
been dissociations and dehydrations and all sorts of in- 
organic weatherings: the crystal is slowly dissolved, and 
the mountains flow into the sea. Likewise the organic 
castle-of-cards is always falling to pieces; there is a see- 
saw of katabolism and anabolism. ‘‘And so, from hour to 
hour, we ripe and ripe, and then, from hour to hour, we 
rot and rot, and thereby hangs a tale.”’ But after allow- 
ing for all the disintegrating and running down, we are 
surely within our rights in saying that there have been 
momentous aggregations and integrations in the past— 
that there is a cosmic tendency or trend in this direction. 
This is especially true of the realm of organisms, where 
natural death itself—the most universal of all vital dis- 
integrations—is sometimes successfully evaded. 


Colonial Creatures 


Postulating the power of growing, itself dependent on 
the organism’s fundamental dynamic quality of accumu- 
lating energy acceleratively up to a limit, we can under- 
stand the disposal of surplus material, so as to form 
various kinds of colonial animals, especially in the sea. 
By budding, and by division of units without subsequent 
separation, there have arisen such aggregates of indi- 
viduals as we see in zoophytes, sea-fans, sea-pens and reef- 
corals, and, at higher grades of organization, in Polyzoa, 
Cephalodiscus and the compound tunicates, both seden- 
tary and free-swimming. Of great interest are those 
multitudinous colonies like the Portuguese Man-of-War, 
in which there are several different kinds of individuals 
showing division of labour, and all so integrated that the 
colony acts as one creature. This is the climax of what 


TOWARDS SOCIALITY 361 


we may venture to call the social trend on the vegetative 
tack of evolution. We cannot follow this line further, 
but it is important to notice that it was particularly well- 
suited for easy-going marine conditions, whereas another 
architectonic way of disposing of abundant growth- 
material—namely, the establishment of a bilateral seg- 
mented body—was well suited to lead the way to the 
conquest of the earth. It is interesting to reflect that the 
acquisition of the kind of body-architecture familiar 
in the earthworm, with its bilaterality and its segments, 
its dorsal and ventral surfaces, its head-end and tail-end, 
was the beginning of our knowing our right hand from 
our left. 


Gregarious Life 


A non-cellular organism multiplies by division, budding 
and spore-forming, and its daughter-units separate off; 
if they remained coherent there would be the beginning 
of a multicellular body, as we see in Volvox, a beautiful 
green ball of 1,000—10,000 cells, sometimes found rotating in 
the water of pond or canal. Many a simple multicellular 
organism disposes of surplus material in the form of buds, 
which separate off, as we see in the fresh-water Hydra; 
if they remained coherent there would be the beginning 
of a colony, as in most zoophytes. Similarly, if the 
members of a physically discontinuous family remained to- 
gether gregariously instead of separating to live inde- 
pendent lives, there would be the beginning of another 
kind of aggregate, the big family, illustrated by a humble- 
bee’s nest early in the year—the big family which passes 
almost insensibly into a community or a herd. From a large 
family of ants all the children of one mother, it is but 
a step to families with grandchildren as well as children, 
to families of several generations, to a combination of 
several consanguineous families living co-operatively, toa 
community of blood relations showing considerable 


362 SCIENCE, OLD AND NEW 


division of labour, and this is almost a society. The true 
animal society is a group of kindred individuals which can 
act coherently and harmoniously as a unity, which has 
a corporate life, which is more than the sum of its parts. 
An ant-hill, a bee-hive, a rookery, a beaver village may 
serve for illustration. The mere living together of a multi- 
tude, like mites in the great cavern of a cheese, does not 
constitute a society; there must be some corporate life. 
When ants go on a slave-making expedition, when beavers 
unite their efforts to make a canal through a big island 
in the middle of a river, when rooks combine against a 
hawk, there is the distinctive social note of esprit de corps. 


Animal Societies 


When we study herds and societies of big-brained ani- 
mals, evolved on an intelligent basis, we feel more or less 
at home. In the merry company of monkeys, sometimes 
uniting in common adventure, in the herds of horses or 
the pack of wolves, in the beaver-village or the city of 
viscachas, among the rooks, cranes and parrots, there is 
an approach to the human. Sometimes there are conven- 
tions which must not be disobeyed; sometimes there is 
combination in defence, attack and enterprise; there is 
often the suggestion of social tissue which does not appear 
foreign to what we know in mankind. There is no doubt 
as to a certain measure of pre-human sociality, and 
among gregarious birds and mammals it is of a type that 
we can more or less readily understand. 


Instinctive Societies 


On the other hand, animal societies on the instinctive 
line of evolution (as among ants, bees and wasps) seem far 
away from us; we cannot breathe their atmosphere. Let 
us take a few glimpses. The division of labour is often 
carried to an absurd length. Thus some individuals 


TOWARDS SOCIALITY 363 


among the honey-ants, which Dr. McCook described 
from the “‘Garden of the Gods” in Colorado, are fed by 
their fellows until they become mere animated honey- 
pots, which are tapped later on. While the Umbrella 
Ant workers are busy in the Brazilian forest cutting discs 
from the leaves, some of their fellows, with enormously 
large heads, simply walk about looking on; they have 
been called ‘‘worker-majors,’’ but no one knows what they 
do, unless their big heads serve as buffers against onslaughts 
on the workers. How quaint is the habit that some 
termites, or white ants, have of keeping wingless reproduc- 
tive members in reserve, complementary kings and queens 
which replace the functional royal pair if need arises! 

similarly, when we consider the subtlety of many of the 
social operations in these instinctive societies—the keep- 
ing of slaves on which the masters become dependent not 
only for food but for the utilisation of it, the organising 
of raids and the engagement in battles, the using of the 
offspring to supply silk for binding leaves together as in 
the tailor ants or to supply drops of elixir as in some 
kinds of wasps, the domestication of other insects, the 
toleration of guests and pets, and, as everyone knows, 
there is a long list of these extraordinary doings, we seem 
to be in a different world, more like a caricature than a pro- 
totype of human societies. In these instinctive societies 
the individual life seems to count for very little; there is 
a fanaticism of self-subordination; large numbers often 
remain non-reproductive. Many an ant-hill is a grim 
warning of the dangers of extreme state-socialism, but as 
to its success in the struggle for existence there is no 
manner of doubt. 


Advantages of Sociahty 


As there are many instances of animal societies at 
various levels, there must be great advantages in the 


364 SCIENCE, OLD AND NEW 


gregarious mode of life. Many small creatures, individ- 
ually contemptible, become safe or indeed irresistible 
when united in large corporate bodies. The Argentine 
ant has in recent years conquered most of the fauna of 
Madeira. Several members of a community working 
together in food-getting may accomplish what would 
baffle single individuals, as when several ants unite to 
drag a big spider to the nest, or when wolves surround 
their prey, or pelicans form a living seine-net for fish. 
From simple advantages such as economising heat when 
large numbers huddle together, to subtle advantages 
such as lessening strain, when one wild goose replaces 
another as leader of the flying phalanx, there are numerous 
obvious advantages in the social mode of life. But it is 
necessary to go further. The division of labour, which 
is often associated with communal life, makes the life of 
the species more effective, as is plain enough from the 
simplest case—which is independent of societies altogether 
—the division of labour between two parents. It is 
almost like a diagram when the hen-bird sits close and the 
male hunts for food. When the division of labour becomes 
specialised in animal societies, as among ants and ter- 
mites, there is the same advantageousness, but there is 
more. The implied relation of mutual dependence be- 
tween the members of the community will tend to foster 
the kin-sympathy and other psychical bonds which origin- 
ally made the community possible. As the society gains 
in stability there will be opportunity for experiment, there 
will be the beginning of a tradition and of external regis- 
tration in permanent products, there will be time for such 
luxuries as fine edifices and play. A milieu will be evolved 
in which wits will thrive. In the struggle for existence, 
which includes all the answers-back that individual 
organisms make to environing difficulties and limitations, 
endeavours in the way of co-operation and sociality are 
evidently rewarded just as are efforts in the direction of 


TOWARDS SOCIALITY 365 


keener competition, and perhaps we may say that there 
is a good deal of secondary benefit, beyond survival, 
thrown in to reward those inclined to be social rather 
than individualistic. The social milieu is one in which there 
is a good chance, to say the least, for the improvement of 
wits and the growth of kindliness, not to speak of the 
appearance of admirable achievements like the wasp’s 
nest, the honey-comb, the termitary and the beaver- 
dam. The society always comes as a shield between the 
individual and the severity of Nature’s sifting. This 
is all too plain in human societies. 


Why Is Not Sociality More Widespread? 


If the social way of life has all the advantages alleged, 
the question naturally arises why it has not been adopted 
by a larger number of types. The answer is to be found 
in certain pre-conditions of sociality—(1) There must be 
some degree of prolific reproduction. Very slowly breed- 
ing animals, unless also very long-lived, will not readily 
form societies. (2) There must be some fineness of brain, 
in the direction both of wits and sympathy; green-flies 
are prolific enough to be social, but they have not got the 
requisite brains. (3) There are certain habits of life which 
preclude sociality. Thus, while spiders are clever enough 
to be social, and there are two or three social species, 
their way of getting a living is intrinsically individualistic. 
One does not expect anglers to fish together in an eleven. 
Thus we see that while the social way of life is very ad- 
vantageous and brings many secondary rewards, it is far 
from being open to all. It is only for the elect. 













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XLV 


INBREEDING AND OUTBREEDING 


367 


“es 





INBREEDING AND OUTBREEDING 


THERE can be no doubt as to the evolutionary im- 
portance of inbreeding and outbreeding in the rise and 
progress of races of plants, animals and men. Everyone 
knows that many primitive peoples were very strict in 
enforcing marriage outside the family or clan (exogamy), 
and while the taboo against consanguineous matings 
cannot have had at that time a biological basis, there 
must have been behind it some definite apprehension 
of the evil effects of inbreeding. On the other hand, in 
certain countries (such as Egypt and Greece) and at 
certain times (e.g. at a high tide of national civilisation), 
close inbreeding or endogamy was sometimes practised 
within castes, and with this there must have been asso- 
ciated a more or less conscious conviction that to gain 
social and cultural advantages it was worth running some 
biological risks. Many years ago Reibmayr wrote a 
scholarly book on the alternation of inbreeding and out- 
breeding in the history of peoples—a biologically inter- 
esting idea. 


Are Cousin-Marriages Harmful? 


In a monograph on the subject (Inbreeding and Out- 
breeding, 1920) Drs. Edward M. East and Donald F. 
Jones have tackled, in the ight of modern biology, three 
questions of great theoretical and practical moment: (1) 
‘‘Do marriages between near relatives, wholly by reason 


369 


370 SCIENCE, OLD AND NEW 


of their consanguinity, regardless of the inheritance 
received, affect the offspring adversely? (2) Are con- 
sanguineous marriages harmful through the operation 
of the laws of heredity? and (3) Are hereditary differences 
in the human race transmitted in such a manner as to 
make matings between markedly different peoples de- 
sirable or undesirable, either from the standpoint of the 
civic worth of the individual or the stamina of the popula- 
tion as a whole?”’ 

If a thoughtful breeder of stock, who is unprejudiced 
by biological literature, be asked for his opinion in regard 
to close mating, he will probably answer that it has its 
advantages and its disadvantages. It is advantageous, 
because, if it is accompanied by the usual judicious selec- 
tion and elimination, it fixes desirable characters and 
leads towards a uniform and stable herd. It is disad- 
vantageous because it is apt to lead to reduction of vigour, 
resisting power, fecundity, and even size. But if the 
breeder is asked, furthermore, whether these disadvan- 
tageous consequences are actually induced by the close- 
breeding as such, or are simply brought to light and 
accentuated by it, he will probably answer that he does 
not go into things so minutely as all that. 


Experiments on Inbreeding 


Yet it is this second question that is vital, and the 
answer to it has been furnished by experiment. For it has 
been proved that the close inbreeding of fine stock, 
associated with the usual selection and elimination, may 
be persisted in for several generations without any unde- 
sirable consequences. Many fine breeds of animals and 
races of plants have had very close inbreeding at their 
beginnings; and there seems to be habitual endogamy 
among bees and ants. Furthermore, it has been shown 
that the direct result of persistent inbreeding is to segre- 


INBREEDING AND OUTBREEDING 371 


gate or isolate within the stock a number of true-breeding 
strains of similar individuals. If there were, to begin with, 
in the inheritance of the herd, say, four distinct hereditary 
factors relative to a particular character, such as the 
colour of the pelage, then the automatic effect of the 
inbreeding will be to isolate four types, pure, as regards 
that particular character. This is a simple theorem in 
Mendelism. But some of the characters which thus 
become isolated may be undesirable ‘‘recessives,’’ seldom 
seen under ordinary circumstances because they are 
hidden by their ‘dominant’ counterparts. The unde- 
sirable albinism, likely to be kept under in conditions of 
exogamy, is isolated and brought to light in endogamy. 
‘“These recessives are the ‘corrupt fruit’ which give a 
bad name to inbreeding, for they are often—very often— 
undesirable characteristics.” 


Close Inbreeding Detects Taints 


This detection of undesirable features by close-mating 
may be utilised by the breeder who knows his business. 
When naturally cross-fertilised organisms are inbred, 
there is sometimes an advance, but there is at least as often 
a disappointing retrogression. Thus, in the case of grain, 
there may be a reduction of productivity to perhaps over 
a half of what it was; in maize there is often a marked 
reduction in size and rate of growth. Now, this lowering 
of the average seems to be due to an outcrop of unde- 
sirable characters which were in the general inheritance 
of the stock (sometimes because of its multiple origin 
from ancestors of diverse merits), but were kept out of 
sight by more favourable characters which dominated 
them. ‘‘Inbreeding tore aside the mask, and the un- 
favourable characters were shown up in all their weakness, 
to stand or fall on their own merits.”’ But if stern elimina- 
tion is practised and the “‘isolated” types with unde- 


372 SCIENCE, OLD AND NEW 


sirable characters are got rid of, the stock will be the 
better of its purgation, and the mysterious quality of 
‘‘vigour”’ can be regained by outbreeding. 

As to this ‘‘vigour,’”’ Darwin was strongly of opinion that 
the gain in constitution derived from an occasional 
crossing was a more important biological fact than the 
loss that often followed close breeding, and modern 
experimenters have confirmed his shrewd judgment. Both 
for animals and plants, the outbreeding often has advan- 
tageous results like those that reward a notable improve- 
ment in nurture. If the crossing be successful at all (for 
there is a seamy side leading to weaklings and sterility), 
there is increase in ‘‘vigour,” resisting power, size and 
other good qualities. The reason for this frequently 
observed ‘“‘hybrid vigour” is probably to be found in the 
pooling of diverse hereditary resources of good quality, 
not in some vague physiological stimulus to the offspring. 
The crossing makes it more likely that a minus on one side 
may be made good by a plus on the other, or that desirable 
dominants may strengthen one another’s hands. We 
have just mentioned sterility, which remains a baffling fact, 
not less puzzling when we know that both inbreeding 
and outbreeding may lead to it. Drs. East and Jones 
suggest that there are two quite different kinds of sterility 
of diverse origin: (1) Inbreeding tends to sort out homo- 
geneous pure strains, and in this sifting out the ability to 
reproduce may be lost; (2) outbreeding may bring to- 
gether two germ-cells too incompatible to allow of a 
continuance of the process of germ-cell making. Thus, 
the number of chromosomes in the two parents (e.g. horse 
and ass) may be too discrepant. But these are deep waters. 


Inbreeding Not Harmful in Itself 


When the same undesirable qualities occur on both 
sides of the house, inbreeding tends to diffuse and exag- 


INBREEDING AND OUTBREEDING 373 


gerate them. Moreover, inbreeding tends to expose, 
and, unaccompanied by stringent selection, to fix detri- 
mental recessive traits which were kept unexpressed in 
circumstances of outbreeding. Nevertheless, the result 
of modern experimenting is clear, that ‘‘inbreeding is 
not in itself harmful; whatever effect it may have is due 
wholly to the inheritance received.’”’ When the inheri- 
tance is on the whole good, ‘‘inbreeding is the surest 
means of establishing families which as a whole are of 
high value to the community.”’ 


Outbreeding Promotes Variability 


A broad survey of the realm of organisms discloses a 
number of great trends of evolution, such as getting out 
of the water, substituting sexual for asexual reproduction, 
and establishing viviparity (flowering plants and mam- 
mals). One of these great trends of evolution is towards 
the securing of cross-fertilisation, though the range of 
the crossing varies within wide limits. Parthenogenesis 
has been tried and self-fertilisation has been tried, but 
some form of cross-fertilisation has prevailed. There 
must be some deep reason justifying this, and the survival 
value of cross-fertilisation lies in the fact that it promotes 
variability. It brings about a greater variety of raw 
material on which selective agencies can work. Similarly, 
for the wider ranges of cross-fertilisation which we call 
outbreeding, the general result of experiment shows 
that this is valuable in promoting variability, both in 
the way of new patterns and new vigour. It is not from 
within inbred castes but from outbreeding in the general 
population that most of the men of outstanding ability 
have come. And if it should be urged that the same 
argument would lead one to expect great things from the 
mating of widely separated types, such as Caucasian 
and Mongolian, the answer is that “‘such unions tend to 


374 SCIENCE, OLD AND NEW 


break apart series of character-complexes which through 
years of selection have proved to be compatible with 
each other and with the persistence of the race under the 
environment to which it has been subjected.” ‘‘The 
changes are too few and the time required is too great 
for the proper recombinations, making for inherent 
capacity, to occur.’’ On the other hand, the intermingling 
of peoples somewhat unlike genetically, but not too unlike, 
has been a frequent factor in progress in the past, and 
must be looked forward to in the future. Always provided, 
of course, that ‘‘the ingredients in the Melting Pot be 
sound at the beginning, for one does not improve the 
amalgam by putting in dross.’ All this has to be applied 
to Ireland and America, Britain and the Balkans alike. 


XLVI 


THE HUMAN HAND 


375 





a 





THE HUMAN HAND 


FEw people know nowadays of “‘ Bell on the Hand,” but it 
was a famous book about the middle of last century and it 
is good reading still. There is abundant entertainment in 
it that has not much to do with the hand, such as Harvey’s 
story of the noble youth who had an opening on the side of 
his chest through which, as a great privilege, Charles I. 
was allowed to behold and touch the heart. The author, 
Sir Charles Bell, was a distinguished anatomist, who 
established the momentous distinction between motor 
and sensory nerves, and the object of his ‘‘ Bridgewater 
Treatise’ was to illustrate from the perfections of the 
hand as an instrument the wisdom of the Creator. This 
was the familiar ‘‘transcendent inference” of the argu- 
ment from design. Paley’s form of the argument has 
ceased to appeal, for Darwin showed, in a general way at 
least, how the fitnesses of the hand have been gradually 
evolved by the secular sifting of successive new departures. 
Yet perhaps we are not wrong in sharing Sir Charles Bell’s 
admiration for the hand, for it is a masterpiece to which 
untold generations of organisms have contributed with a 
remarkable combination of plasticity and retentiveness, 
“testing all things and holding fast that which is good.”’ 
Even apart from any “‘transcendent inference”’ the hand 
is worthy of our admiration, most of all when considered 
as the outcome of a long evolutionary process; and so we 
turn from Sir Charles Bell’s book of 1833 to Professor 
Wood Jones’s book of 1920 (The Principles of Anatomy 
as seen in the Hand.) 


377 


378 SCIENCE, OLD AND NEW 


A Generalised Hand 


Man with his nimble brain can do so many different 
things with his hand that no one can be surprised at the 
widespread idea that it is a very highly evolved instrument. 
This is true in a sense, but what Professor Wood Jones 
insists upon is that the human hand is very generalised. 
That is evident at a glance, when we compare it with a 
highly specialised hand like that of a bat or of a mole, but 
it admits of detailed proof. Thus the number of digits 
is five, which is the primitive number, for although the 
horse has only a single complete digit on each limb, we 
know that it is descended from ancestors with five, and 
although some of the extinct aquatic Ichthyosaurs had six 
or more digits, there seems no doubt that this condition 
was derived (e.g., by splitting of the third finger) from the 
pentadactyl type in most terrestrial reptiles. Almost the 
only specialisation of the human hand is in the mobility 
of the opposable thumb, and that is practically a general 
character of monkeys and apes. ‘‘The human condition 
of complete pentadactylism is,” according to Professor 
Wood Jones, ‘‘a feature which stamps this part of man’s 
anatomy with the hall mark of primitiveness.’’ What is 
true of the number of the digits holds good also in regard 
to the proportions of the fingers, except that there is in 
some people a marked elongation of the index, and in 
regard to the finger-joint-formula. Man’s foot is ex- 
tremely specialised, man’s hand is very generalised. 

In the palm of the hand or metacarpal region there is a 
slight specialisation, namely, the stoutness of the bone 
which bears the index finger, and this our authority inter- 
prets as ‘‘definitely related to the use of the index finger as 
a companion to the mobile thumb in the act of picking up 
objects and grasping them.’”’ Similarly, man’s wrist or 
carpus, though extremely primitive, has the peculiarity 
that one of its eight little bones—the os centrale—has 


THE HUMAN HAND 379 


disappeared as a separate entity. Its fusion with one of 
its neighbours, the scaphoid, probably gives greater 
stability at the base of the important index finger. It is 
an eloquent fact that in the gorilla and chimpanzee, where 
the index finger has also attained to some importance, the 
fate of the os centrale has been the same as in man—it 
has fused with the scaphoid. In the orang and gibbon 
and in most monkeys there is a separate os centrale, as in 
mammals generally. This little bone is a straw which 
shows how the evolution wind has blown. 


The Lines on the Hand 


Many credulous people are much interested in the lines 
on the palm of the hand, and are intimately acquainted 
with the individual peculiarities of their ‘‘line of heart,” 
‘line of head,” ‘‘line of life,” and the others. But the lines 
have also a biological interest. ‘They indicate lines of 
comparative skin rest, where the skin is anchored to the 
underlying tissues; they are crease lines suited to give the 
greatest freedom of movement to the joints. They must 
have been established very long ago, for there is a general 
human pattern of lines, quite different from that of apes or 
monkeys, and the main creases appear very early in ante- 
natal life before there is any movement of the hand. But 
the other side of scientific palmistry is not less interesting, 
that within the limits of a general human pattern there is 
great individual variability in the finer ramifications, and 
likewise great individual modifiability according to the 
work we do with our hands, or the games we play. 


Finger-Prints 
Entirely different, of course, from the flexure lines we 


have just spoken of are the papillary ridges. These are 
delicate thickenings of epidermis separated by furrows; 


380 SCIENCE, OLD AND NEW 


they are disposed in regular patterns of parallel lines, 
concentric circles, and close spirals; they show the open- 
ings of sweat-glands along the crest of the ridge. The 
patterns formed by the papillary ridges do not change 
throughout life; they are established before the ante-natal 
chapter is half over; they differ somewhat in different races 
and they are so strikingly individual that their practical 
importance as a means of identification, first pointed out 
by Dr. Henry Faulds in 1880 and afterwards emphasised 
by Galton, is nowadays generally recognised. Professor 
Wood Jones writes. 


The print of any individual finger-tip may be recognized 
with certainty among thousands of such prints, and when we 
remember that each of the ten digits shows its own peculiar 
pattern and its own distinctive minutie, the chance of coin- 
cidence in the patterns of any two individuals when the print 
of more than one finger is examined is practically negligible. 


It seems likely, however, that the patterns are in some 
measure hereditary characters. As to their significance, 
their wide occurrence among mammals with the power of 
gripping surfaces and objects, points to the conclusion 
that they ensure ‘‘a firm, precise, and _ sensitive 
apposition.”’ 


Nails 


There is much that is biologically interesting in the 
nails which protect the sensitive tip of the digit, serve for 
scratching, and increase certain kinds of grip. The most 
primitive nails are those of some amphibians, and they are 
flat plaques; so the question rises whether our nails repre- 
sent a retention of a very primitive condition or a flatten- 
ing of the common arched claws of most mammals. They 
arise in the individual as cornifications of the epidermis 


THE HUMAN HAND 381 


below the surface, and the covering which originally hides 
them persists as the irregular margin of transparent skin at 
their base and the ‘‘sole pad’’ beneath their free edge. 
They grow throughout life, the exposed area being nor- 
mally renewed about every eighty-seven to one hundred 
and twelve days. They are to some extent indices of 
health, and Professor Wood Jones favours the view that 
the familiar little white spots are partly due to worry! 
Our own experience is more commonplace. 


The Hand in Evolution 


The muscles and tendons, the connective tissues and 
blood-vessels of the hand are just as interesting as the 
bones and surface-characters, but they are not so readily 
dealt with. On the whole, they bear out the thesis that 
man’s hand is generalised. As Aristotle, Galen, Sir 
Charles Bell, and Professor Wood Jones have all recog- 
nised in their several ways, the excellence of the human 
hand is in being a generalised tool which the fertile brain 
can use in a hundred different ways. ‘‘It is not the hand 
which is perfect, but the whole nervous mechanism by 
which movements of the hand are evoked, co-ordinated, 
and controlled.’”’ But this, again, requires to be corrected 
by two considerations: first that a mobile testing hand, 
relieved from doing duty as an organ of support, as Pro- 
fessor Wood Jones made so clear in his Arboreal Man (1916) 
was closely correlated with the development of the cere- 
bral cortex, and, secondly, that as the muzzle region 
of the head became less marked and less utilised for testing 
things by actual contact, the hand became increasingly a 
sense-organ. In enabling man to test the qualities of his 
surroundings—texture, shape, sharpness, dimensions, 
weight, pressure, vibrations and temperature—the hand 
has played an incalculably important part. In spite of its 
generalised fundamental features, man’s hand is, as 


382 SCIENCE, OLD AND NEW 


regards its sensory nerve-endings, more specialised than in 
any other creature. It has been one of the great gateways 
of knowledge, and in manipulative art it has been one of 
the chief instruments of the soul. 


XLVII 


MAN’S PLACE IN NATURE 


383 


Ye Leal Cats 2 vay Pa Mah he ent ‘Ss 
x an e me a! rs ‘ ' 





5) ry al fe ja 4 py lan G 7 ; ware : 
‘ one nie 4) 4 re ; ¢ van A “ah 


‘ 





MAN’S PLACE IN NATURE 


ACCORDING to Dr. John Lightfoot, an eminent Hebrew 
scholar in his day, and likewise Vice-Chancellor of the 
University of Cambridge, man was created by the Trinity 
on October 25, 4004 B.C., at nine o’clock in the morning. 
According to Professor Sir Arthur Keith, Conservator of 
the Hunterian Museum, ‘‘man had reached the human 
standard in size of brain by the commencement of the 
Pliocene period . . . that is to say, about one million 
years ago.” In all probability the truth is between these 
extremes, but nearer Sir Arthur Keith’s estimate than Dr. 
Lightfoot’s. In his interesting and challenging book, 
Man and the Attainment of Immortality (1922) Professor 
James Young Simpson writes: 


When we realise that flints of indubitable human workman- 
ship are found in the drift gravel of the Somme at a distance 
of 100 feet above the present level of the river, and then con- 
sider how slowly the river is being lowered by erosion, we begin 
to have some sense of the vast period that has elapsed since 
man first dropped these implements by the water’s edge, and 
are ready to believe that 400,004 B.C. is a more approximate 
date to his appearance than 4004. 


What is certain is that man of the modern type appeared 
on the scene very long ago, and there were tentative men 
before that. 

385 


386 SCIENCE, OLD AND NEW 
Man’s Solidarity with Mammals 


But there is, of course, an even deeper difference between 
Dr. Lightfoot’s view and Sir Arthur Keith’s. According 
to the former, man was created one morning by the 
Trinity, which means that he arose in a fashion which 
cannot be described in scientific terms. According to the 
modern view, man arose ‘‘naturally,” a mutation or 
transilient variation in all probability, yet continuous 
with a pre-human ancestry. Man was solidary with a 
Simian stock, and arose from Primate parents who begat 
him; and there is no reason why he should be ashamed of 
his poor relations. If there is great excellence in him— 
the achievement, there must have been the right stuff in 
those by whom it was achieved. 


Man’s Ancestry 


No naturalist supposes that the human stock was 
derived from any existing ape. That is out of the ques- 
tion. But the facts point to the divergence of mankind 
from a stock which diverged on another line to give rise 
to the larger Anthropoid Apes—the Orang, the Gorilla, the 
Chimpanzee, and some extinct forms. The human branch 
and the ape branch sprang from a stem common to them 
both; they are collaterals. 

Another important fact is what we might call the suc- 
cessive segregating of the more progressive. Very long 
ago—perhaps two million years ago—in the Eocene Ages, 
there was a stock of primitive, somewhat generalised, 
monkeys. For the time they occupied the top of the tree 
—the genealogical tree. But first of all, there was a sep- 
arating off of the branch whose twigs are the New World 
Monkeys. Later on the same thing happened for the Old 
World Monkeys. That left an Anthropoid main stem 
with a vigorous growing point. But the segregating 
process went on. Another branch diverged—that of the 


MAN’S PLACE IN NATURE 387 


smaller Anthropoid Apes, the Gibbon, the Siamang, and 
some extinct forms. Then came the separating off of the 
larger Anthropoid Apes, leaving the main stem Humanoid. 
But even then the segregating process continued, for there 
diverged Pithecanthropus the Erect, the slouching men of 
Neanderthal, and the type represented by the Piltdown 
skull, leaving at last the purified main stem—the modern 
man type—from which have diverged Africans, Austra- 
lians, Mongolians, and Europeans. ‘The point is that even 
the Neanderthalers do not seem to have been our ancestors 
but only a collateral species. They probably represent a 
blind alley in evolution except in so far as their virtues may 
have been continued by crossing with Homo sapiens. 

It is not to be supposed that all the fossil remains of man 
are off the main stem, for that would leave the main stem 
an unknown quantity; but there appears to be general 
agreement among experts that Neanderthal man, for 
instance, was no ancestor of ours. He was one of the 
early tentative men, who shared in the struggle but did 
not inherit the promises. Nor must we allow ourselves 
to confuse the segregation of the less promiseful with the 
ordinary eliminative operation of Natural Selection. 
The monkeys diverged, leaving the main line the better 
for their absence, but there was no failure on their part. 
They have evolved successfully on a line of their own. 
Similarly with the Anthropoid Apes. Though there are 
extinct genera of apes, as among monkeys, the Anthro- 
poids have held their own, and they have many admirable 
qualities. In the case of the Neanderthalers there was 
divergence from the main stem, but there was also, 
unluckily, extinction—as a distinct race at any rate. 


Factors in Man’s Emergence 


As to the factors leading to the emergence of the human 
type, we remain immensely ignorant. But we must not 


388 SCIENCE, OLD AND NEW 


be impatient, for evolutionary inquiry is still very young. 
It is probable that an arboreal apprenticeship on the part 
of our pre-human ancestors counted for much. It wasa 
great step when the hand ceased to be a supporting limb 
and became a free hand—all the more valuable because it 
remained generalised, able to do all sorts of things. The 
emancipation of the hand, which made it available as a 
food-capturing organ, allowed of the reduction of the 
muzzle; and that meant a possibility of great increase 
in the cranial region or brain-case. No doubt there was a 
correlated advance in the development of the cortex of the 
fore-brain, so that it became easier for the animal to make 
judgments in jumping from branch to branch, to establish 
associations between endeavours and results, and to store 
memories. Germinal variations in the direction of a more 
highly developed cerebral cortex would be approved of in 
the everyday sifting and would become part of the racial 
inheritance; and thus was progress made. 

Another factor was the capacity for sociality, a capacity 
which was pre-human in origin, but came to its own 
increasingly as the Humanoid brain grew finer, or, to put 
it in another way, as the psychical side became more 
dominant. As was said wisely long ago: ‘‘Man did not 
make society; but society made man.” 

Some authorities rebut the speculation that our pre- 
human ancestors served an arboreal apprenticeship, but 
the theory has much to commend it. When the Human- 
oids, with their free hands, their enlarged cerebral cortex 
or neopallium, and their capacity for co-operative action, 
had resources sufficient to enable them to stand up to 
to Carnivores and other enemies, they left the trees and 
became once more terrestrial—and Men. But they were 
bipeds now, save when babyhood recapitulates the past, 
or when some shock or degeneration involves a slipping 
down the rungs of the steep ladder of evolution. With 
the upright attitude there is probably to be associated 


ee ee ee 


— 





MAN’S PLACE IN NATURE 389 


the further evolution of the voice; and when language 
began, as a means of social intercourse and mutual cor- 
roboration, sociality would grow apace. All these pro- 
cesses work in spirals: sociality favours variations in the 
direction of language, but language makes progress in soci- 
ality more practicable. Evolution works in virtuous circles. 


The Ascent of Man 


At different times in the course of evolution there have 
been differences in the sieves that determined survival. 
There has been an evolution of sieves as well as of the new 
material submitted for sifting. Usually the sifting has 
had reference to the qualities of importance in the quest 
of food—and we have not yet got beyond that. But 
sometimes the emphasis was laid on fertility and at other 
times on the strength or swiftness which made it possible 
for an animal to baffle its enemies. More and more as we 
ascend the series the decisive factor is to be found in wits 
or cunning rather than in strength or fertility. One of the 
many good points in Professor J. Y. Simpson’s book, Man 
and the Attainment of Immortality (1922), is the insistence 
on the changes, throughout the ages, in the criteria deter- 
mining survival. It is a good point as long as it is not 
over-emphasised. But it must be borne in mind that on 
the whole the fundamental criteria persist—though with 
varying emphasis—all along the line and all the time. 
There must always be success in the quest for food; there 
must always be health (we are excluding parasites from 
consideration); there must always be ability to hold the 
gate against enemies and keep a place in the sun; there 
must always be a birth-rate sufficient to counteract the 
death-rate. 

Yet when all this is said, we feel that for primitive man, 
with his growing brain and vocabulary, the next most 
essential quality was a strong kin-instinct and a capacity 


390 SCIENCE, OLD AND NEW 


for team-work. What was all-important, given the big 
brain and language, was a willingness to subordinate self 
in playing the game. In short, man’s survival depended 
largely on ethical qualities. In the evolution of these, 
the prolonged infancy of the offspring doubtless played an 
important part. As Lucretius said long ago, ‘‘Children by 
their caresses broke down the haughty temper of their 
parents.” 

It has often been said that such subtle human qualities 
as musical talent cannot be accounted for along the lines of 
the Darwinian theory, that is by the natural sifting of new 
departures. But we doubt if there is any great difficulty 
here. In the first place, no one is inclined to postulate 
any special spiritual influx to account for the evolution of 
the notable musical talent of birds. It has its survival- 
value in connection with mating and as an expression of 
very vitalemotion. In the second place, there is no doubt 
as to the integrative value of music in the social endeavours 
of mankind. Furthermore, it is true throughout all 
organic evolution that a new departure, not in itself of 
immediate utilitarian significance, may be correlated with 
some more obviously justifiable variation and be carried in 
the wake of this into safety. It is easy to imagine, if we 
cannot prove, that musical mutants might survive, to 
start with, not because they were musical, but for more 
commonplace reasons. 

What happened eventually—if we dare use such a word 
in reference to a race so relatively young as mankind—was 
that man became conscious of his own evolution and began 
to take a hand in determining its trend. Many a time, 
we believe, wide-awake organisms have been active agents 
in their own evolution, e.g., in choosing the environment 
that suited them; but man’s rational, or more or less 
rational, selection is a new feature that has made all things 
new. Persistently, though with chequered success, he has 
been eliminating the factors that make for disease, dis- 


MAN’S PLACE IN NATURE 391 


harmony, and distress. But now there is in his eyes a 
more positive ideal—the ideal of fostering health, har- 
mony, and happiness, so that in this world there may 
come about an all-round realisation of the true, the beauti- 
ful, and the good. Thus man’s life as a social organism 
will become increasingly a satisfaction in itself. Jn hoc 
signo laboramus. 


My 





XLVITI 


THE HUB OF CREATION 


393 


wt 





THE HUB OF CREATION 


IF we can imagine Martian naturalists visiting the 
earth before the emergence of any of the Hominide (Man 
and tentative men), we can also imagine that they would 
be greatly interested. The world is full of artistic master- 
pieces, fascinating ingenuities of organisation, and intricate 
interweavings that make a pattern. Almost every- 
where the Martians would find order and fitness; almost 
everywhere the Martians might hear snatches at least of 
‘““an onward-advancing melody,” as the philosopher Lotze 
phrased it. The earth without man is like a cathedral 
without spire or tower—but a cathedral. It is full of 
wonders that angels might delight to look into. 


Man as Crown 


What gives the world beauty and scientific interest is 
not the presence of man, for we can imagine the visit of 
the Martian explorers to a beautiful and interesting pre- 
Tertiary earth; and, besides, it is idle to pretend that there 
is not some infra-human delight in beautiful sights and 
sounds, that there is not some infra-human regional sur- 
vey! But the important fact is that when man emerged, 
Animate Nature gained a new significance. In him the 
mind that had been struggling through all ‘‘the spires of 
form’’ found some measure of emancipation. 


395 


396 SCIENCE, OLD AND NEW 


The Logos became articulate in a new language. And 
as man began to understand Nature and to see himself 
objectively as her child, he also came to see in a dim way 
that he was the result of ages of groaning and travailing, 
that he was no episodic phenomenon in a long chapter of 
accidents, but a climax towards which thousands of 
events had conspired. We do not mean that man has not 
a long way to go yet; but we adhere to the philosophy 
which regards man as a flower that illumines the whole 
plant—even the roots which go deeply into the ground. 
The broadly-laid foundations—all the balance and in- 
tricacy of Nature—have made man possible; and it looks 
as if he were the outcome of a well-considered plan. 


Man ‘‘with Worlds to Attend Him” 


We make the philosophical postulate that man, as the 
finest expression of Nature’s evolution, throws light on all 
his antecedents. 

We find scientific evidence of a succession of prepara- 
tions that made higher organisms, and eventually man, 
possible; we see a balance established throughout ages 
which made a lofty superstructure stable; we discern a 
multitude of little circumstances that make the earth 
what one might call ‘‘friendly” to man. The ancillary 
creatures were not exactly created for man, but they are 
parts of a coherent system of which man is at present the 
highest expression. 

Following a scheme which Sir Ray Lankester suggested 
long ago, we wish to illustrate the manifold practical inter- 
relations which have been established between man and 
animals. The subject is almost inexhaustible, but there 
is often an advantage in a bird’s-eye view. It will be seen 
at a glance that some of the intersections between man’s 
vital circle and those of other creatures are very ancient, 
and others very modern. They are always changing. 


THE HUB OF CREATION 397 
Edible Animals 


The first procession is that of animals captured for 
food, and it is a motley crowd. Deer and antelopes, 
rabbits and hares, pigeons and partridges, frogs from 
France, and all the food-fishes of the sea and the fresh 
waters. Squids from the Mediterranean, snails from 
Italy, cockles and mussels, oysters and clams from our 
own shores. Crabs and lobsters, shrimps and prawns; 
locusts served with wild honey, juicy grubs from the palm 
trees, and white ants for the Hottentots. Once a year the 
Samoans have a feast of headless palolo-worms which 
make the sea like thick vermicelli soup. The roe of the 
sea-urchin is a common Mediterranean delicacy, and the 
sea-cucumbers or béche-de-mer form an important com- 
modity in the Far East. Characteristically enough, the Jap- 
anese eat dried jellyfish, but no one has been able to make 
a meal of sponges. The nummulites, common as fossils 
in some parts of Egypt, are called ‘‘Pharaoh’s bean,” but 
that is just a little joke. 


Amimal products 


The second procession is that of animals captured not 
for the sake of food directly furnished by their flesh, but 
for the sake of other products, which are sometimes 
edible. Here we have the baleen whales with their whale- 
bone plates and their oil, the elephants with their ivory 
tusks, the wild asses whose skins are made into drum- 
heads, the beavers yielding the sweet-scented castoreum 
and the hats of long ago, scores of mammals giving up 
fur and hide. Here come feathers for arrows and the 
angler’s flies, for the savage’s head-dress and the lady’s 
hat; the crocodiles give us leather bags and the turtles 
combs; inedible fishes yield glue and fertilisers; the 
cowries are for money and the big oysters for mother-of- 


398 SCIENCE, OLD AND NEW 


pearl; the cantharid beetles make blisters for our skin. 
This procession would fill the whole page if we let it. 

The third procession is a short one, consisting of those 
animals that man has more or less domesticated because of 
their direct or indirect utility. Here come dog and horse, 
sheep and cattle, goats and reindeer, pigeons and poultry, 
ostriches and pheasants, silk-moths and honey-bees, and a 
few more besides. 


The Scavengers 


The fourth procession consists of those creatures that 
favour man’s operations. Here are the earthworms that 
have made the fertile soil and the flower-visiting insects 
that secure cross-pollination. Here are the scavengers 
that keep the earth clean—the sexton-beetles and the 
carrion-loving birds. But soil-making and seed-making 
are the two greatest benefits. 

The fifth procession is that of man’s enemies—a much 
smaller band than it used to be. Here are the beasts of 
prey with which primitive man struggled, learning many 
a valuable lesson in stratagem, patience, and courage. 
The poisonous snakes take a long time to pass, rowing on 
the ground with their ribs, and still biting man’s heel. 
Crocodiles, alligators, and gavials levy their toll on the 
unwary, and sharks still follow the drifting wreckage or 
the divers who seek for pearls. Hercules seems to have 
practically finished off the octopus or hydra, though oc- 
currences such as Victor Hugo describes in his Toulers of 
the Sea are still within the bounds of the possible. 

Poisonous insects like hornets may still be formidable, 
and man must be careful lest he fall into the hands of the 
army-ants. But the insects that hinder man most are 
those whose bites serve for the injection of microbes, as 
in the case of the malaria-laden mosquito. This leads us 
to notice that in the course of ages the size of man’s 


THE HUB OF CREATION 399 


enemies has dwindled greatly. Indeed, his worst enemies 
are in a sense those of his own household, the internal 
parasites like hookworm and bilharzia, or the minute pre- 
datory animals which cause malaria, syphilis, and sleeping 
sickness. But even these Lilliputian enemies are being 
conquered by man. 


Pests 


The sixth procession is made up of animals which in- 
jure man indirectly, by attacking useful animals and useful 
plants. Here are the pests that destroy man’s animal 
stock or his crops. One thinks of the voles that some- 
times eat up every green thing on the farm, or of the 
locusts that find a country a garden and leave it a desert. 
The procession is marked by a dense cloud of injurious 
insects, from cockchafers to cotton-weevils, from wheat- 
midges to warble-flies. Besides these there are worm- 
parasites in prodigious numbers, often doing serious 
damage among animals and plants alike. It is plain that 
inimical animals can do much more harm among herds or 
crops than in open Nature, for many victims are found 
within a short radius. The Colorado beetle was unimpor- 
tant till man planted great fields of potatoes. 

The seventh procession consists of animal enemies 
which injure man neither directly, nor through his stock 
and crops, but by getting at his stores or permanent prod- 
ucts. Thus the termites or white ants in warm countries 
often cause serious loss and inconvenience, for they de- 
vour everything wooden and everything that approaches 
the wooden, from the books in the library to the corks in 
the cellar. Everyone knows the havoc that is caused by 
rats and mice, which often spoil much more than they eat. 
Of great importance also are the weevils and other beetles 
that feed on stored corn, or the larve of the flour-moth that 
devour army biscuits. 


400 SCIENCE, OLD AND NEW 
On Man’s Side 


The eighth procession makes us more cheerful, for it is 
made up of those animals that keep a check on the three 
contingents in front of them. In other words, they are 
man’s indirect friends. Thus the birds of prey keep down 
the voles; the hedgehogs keep down the slugs; the lap- 
wings devour the wireworms and leather-jackets; the ich- 
neumon-flies lay their eggs in the caterpillars; the spiders 
catch the scale-insects; the lady-birds levy toll on the green- 
flies; the water-wagtails are fond of the small water-snails 
that harbour the juvenile stages of the liver-fluke; and so 
on through a very long list. 

There is no object in elaborating the point, which is 
just this, that the circle of man’s life cuts many other 
circles. He is the hub of a complex wheel, but it is a wheel 
within wheels. He is part of a web of life which he con- 
tinues to fashion, and the success of his weaving depends 
on his understanding. 


XLIX 


INCREASE OF KNOWLEDGE, INCREASE OF SORROW 


401 





INCREASE OF KNOWLEDGE, INCREASE OF 
SORROW 


A CRITICISM is sometimes advanced, in regard to the 
progress of science, that it makes things worse, not better. 
Instead of making, as Bacon said, for ‘‘the glory of God 
and the relief of man’s estate,’ science is accused of filling 
human life with new horrors. Increase of knowledge is 
increase of sorrow, they say. Science is always up to some 
new devilry! 


Science and Invention 


How are we to meet this reproach? Part of the answer 
must lie in distinguishing between scientific discovery and 
subsequent invention. ‘The chief end of science is under- 
standing, and there can never be too much understanding, 
though it may be abused. Science primarily means Light, 
and the more light the better, even if it be used for evil 
purposes as well as for good. Science in so far as it is 
luminiferous is beyond all criticism, except, of course, that 
it sometimes makes mistakes; but that cannot be said of 
science as fructiferous, to use Bacon’s words again. The 
evil is not in the scientific discoveries in the strict sense, 
but in some of the inventions which man has sought out. 
Yet this is only part of the answer, for the distinction be- 
tween discovery and invention is not hard and fast; and 
many great discoverers, like Lord Kelvin, have also been 
great inventors. 


403 


404 SCIENCE, OLD AND NEW 


Everyone admits that modern chemistry has made the 
world much more intelligible than it was before the days 
of Lavoisier. Scores of puzzles have been solved, and 
man’s understanding of the life of his own body has made 
great strides. It is difficult for us to realise that before the 
time of Lavoisier—who was beheaded during the French 
Revolution—no one understood what breathing meant. 
But chemistry has grown from more to more, and the 
chemist has become a creator. From simple elements, as 
everyone knows, he can build up complex carbon-com- 
pounds; he can make natural substances artificially, which 
may be great gain when these natural substances are very 
scarce or cannot be procured except at great cost. He can 
also make new things which the world never saw before. 


Coal-tar Beauty 


Now we are not prepared to say that the making of, let 
us say, aniline dyes out of coal-tar has added to the beauty 
of the world; our point is that the making of these dyes 
was a natural practical outcome of theoretical advances in 
chemical science which have illumined the world. More- 
over, while it does not seem to us that the invention of 
modern explosives has added to the welfare of the nations, 
it is only fair to recognise that there are other inventions, 
say chloroform, which are on the same general line of 
chemical synthesis. Adrenalin is a potent substance, of 
very distinct use in medicine and surgery; it is made in 
small quantities by the suprarenal glands; there is obvious 
gain in the practical invention which now produces it 
artificially. 

It is not science that should be blamed for devilish in- 
ventions; it is the heart of man that is desperately wicked. 
Strychnine is a very valuable medicine; those who dis- 
covered it are not to be blamed because it can be used as a 
deadly poison. 


INCREASE OF KNOWLEDGE AND SORROW 405 


Human society is such a complex business, and the laws 
of its evolution are so inadequately known, that it is ex- 
tremely difficult to foretell what may be the results of this 
or that application of science. Who can tell what will 
happen if one pulls a thread out of a woven fabric?—and 
a human society or a civilised state is a very intricate 
web of life. 


Not Enough Science 


What is wrong is not that we have too much science, 
but that we have not enough for the complexities of the 
situation. It is likely that a big change in human activi- 
ties will have correlated effects that are deleterious. It is 
very easy-going to suppose that because a new develop- 
ment was bound to come, and is sound on the whole, it 
may not in some way justify the criticism that increase of 
knowledge may be increase of sorrow. Even when the 
new development means an increase in the supply of 
wholesome food, we must be careful to inquire into all the 
human cost of the process; and it is also legitimate to in- 
quire whether an increase in the possibility of ‘‘more 
people’’ is necessarily an unmixed blessing to the human 
race. The world is rapidly becoming very full, and it is by 
no means certain, to put it mildly, that it is being filled 
with people of the right sort. 


Real Progress 


The problem is how to anticipate the criticism that more 
science often means more sorrow. And what we have 
suggested may be re-stated in a more concrete way. The 
late Sir William Ramsay once said that real progress con- 
sisted in more economical use of energy—a very charac- 
teristically chemical utterance. If a new departure is 
very wasteful of natural energies, it is at once condemned. 


406 SCIENCE, OLD AND NEW 


But a new development which made more of available 
energies than ever before would not necessarily be com- 
mended by a biological tribunal. The lower must be 
judged by the higher, and the question would have to be 
pressed whether what was physically commendable was 
likewise good for the health of the workers and the com- 
munity. 

Similarly in regard to some biological proposals, such as, 
let us say, giving incurables a euthanasia, or sterilising 
undesirables, they may be excellent—we do not say that 
they are—from the purely biological point of view, but 
that is not the last word. Man is more than an animal; 
he is a reasonable social person. And the question must 
be faced whether these eliminative proposals, supposed 
for the sake of argument to be biologically sound, are also 
sound psychologically and socially. Do they do no vio- 
lence to the spirit of man? Is social sentiment ready for 
them ? 


L 


THE BEAUTY OF ANIMAL LIFE 


497 


Venee 


Whe eoead Ae 
: " a : 
Oe tA om 


i. 





THE BEAUTY OF ANIMAL LIFE 


WHat happens in us when we enjoy a beautiful animal 
like a peacock or an antlered stag or a scallop shell? There 
is a physiologically pleasant activity in our eyes and 
nervous system, and to this there is linked a joy. Through 
the nervous system—especially the sympathetic nervous 
system—the pleasant excitement overflows into outs and 
ins of the body. It seems to influence the beating of the 
heart, the breathing movements and other activities, 
either directly or through the regulative system of such 
ductless glands as the suprarenal body. For Wordsworth 
was a better physiologist than he knew when he said: 
““My heart leaps up when I behold a rainbow in the sky,” 
or again, ‘‘And so my heart with pleasure fills and dances 
with the daffodils.’”” To some people an ugly creature, 
deformed by man, is an actual source of pain, just likea 
discordant noise. 


The Sensory Thrill 


In some cases, as when we lazily watch the wind making 
waves on the hayfield, or the river flowing past, we may 
not get beyond the sensory thrill. What we see excites in 
us pleasant sensations, which may be enjoyed without 
much accompaniment in the way of joyous feeling. But 
in the great majority of cases we advance to a higher level 
of esthetic appreciation. 


409 


410 SCIENCE, OLD AND NEW 


We watch the gulls gliding against the wind, after a 
succession of powerful strokes, and the idea of fitness or 
adaptation flashes through our mind. We do not dwell on 
it, that would be science; but we cannot shut out its in- 
fluence. We see the kingfisher dart up the stream, like an 
arrow made of a piece of rainbow, and we suddenly re- 
member when we saw it last. We do not dwell on the 
memory, that would be reminiscence; but we cannot shut 
out its influence, and it probably adds to our joy. At an- 
other time there is an association of ideas. The swallows 
suggest migration and the circumvention of the seasons. 
The V-shaped phalanx of wild geese flying north suggests 
the misty islands and a waste of seas. In short, the 
esthetic thrill is strengthened by ideas. 


The Imaginative Touch 


But there is a third level to which we rise occasionally, 
when we are influenced by sympathetic fancy. We pro- 
ject ourselves into what we see and enjoy its qualities 
vicariously. The soaring lark is an emblem of freedom. 
The salmon rising clean out of the water at the falls is 
significant of the insurgence of life. The spider’s web is 
not only beautiful in itself; it gives us a responsive thrill 
that another living creature has attained to such a mas- 
terly use of materials. Life answers proudly to life. 

The imaginative touch brings us to the confines of poetic 
fancy. Thus William Blake wrote :— 


And before my way a frowning thistle implores my stay, 
What to others a trifle appears 

Fills me full of smiles or tears; 

For double the vision my eyes do see, 

And a double vision is always with me. 

With my inward eye, ’tis an old man grey, 

With my outward, a thistle across my way. 


THE BEAUTY OF ANIMAL LIFE 411 
In What 1s Beauty Expressed? 


The qualities in animals that impress us as beautiful 
may relate to form, colour, and movement. There are 
forms that sing and lines that flow. Experiments with 
children show that preferences exist in favour of certain 
shapes, such as an ellipse with its axes in the proportions of 
5:3. The eye is not fond of complicated shapes that are 
conundrums. We like lines that conspire to one effect. 
We enjoy the regular increment of the logarithmic spiral 
—an expression of orderly growth—which crops up so 
frequently in organic nature. We see it in spiral shells, 
in fir-cones, in the arrangements of young leaves in a bud, 
in the twisted horns of the antelope, and in many other 
expressions. Our theory is that the objective basis of 
form-beauty is in the rhythmic orderliness of normal 
growth. An unhealthy monstrosity, which would not be 
tolerated in wild nature, is bound to be ugly. 


Daring Experiments in Coloration 


In humming-birds, parrots, and birds of paradise, in 
butterflies, spiders, and coral-fishes, we find the most 
daring experiments in coloration. But they never seem to 
be wrong. These colours are often due to pigments—the 
waste-products or by-products of wholesome and unified 
living. Or, asin many shells that have no pigment at all, 
they are due to the regular occurrence of fine lines or fine 
plates which produce iridescent colours. And we may 
think of the regular occurrence of fine lines and laminze 
as the ripple-marks of internal tides of rhythmic growth. 
In many cases pigmentary and structural colours are com- 
bined, as in peacocks’ feathers. There are some luridly 
coloured skin-diseases, but they are always discordant. 
The exception proves the rule; they bear the stigma of 
their intrinsic disorderliness. Beauty is the hall-mark 
of the healthy. 


412 SCIENCE, OLD AND NEW 


Melody of Motion 


When we watch jellyfishes throbbing in the tide, or a 
line of porpoises simulating a great sea-serpent, or the 
butterflies fluttering over the meadow, or a troop of cuttle- 
fishes keeping time with one another in the water, or the 
mayflies rising and falling in their evening dance, or the 
flying-fishes volplaning before the steamer, or the aérial 
evolutions of lapwings, we enjoy a sort of melody of mo- 
tion; and this is a third factor in the beauty of animal life. 
The climax is when an animal, beautiful in form and 
colouring, is also beautiful in its eurhythmic movements. 


Asthetic Sense 


In a few cases, such as bower-birds, there is obvious 
pleasure in brightly coloured objects. To decorate their 
honeymoon bower, these birds collect silvery leaves, 
gorgeous pods, beautiful shells, and the like; and there 
seems no reason to deny them an esthetic sense. Then 
there are many cases where the male animals at the court- 
ing season show off their decorativeness, and it may be 
that their desired mates are not indifferent to the beauty- 
factor in the attractive tout ensemble of the rival suitors. 
Thirdly, it is difficult to believe that creatures that often 
fashion masterpieces, such as many nests are, have not 
some measure of the artist’s joy. 

When all this is allowed for—and we doubt if anyone 
has yet allowed for it enough—the question rises why 
animals are so beautiful in detail, and often very remark- 
ably beautiful in their internal and quite hidden archi- 
tecture. George Meredith has given us most of the 
answer in the simple words: ‘‘The ugly is only half-way to 
a thing.”’ In Wild Nature we have to do with finished 
workmanship, with structures that have stood the test of 
time, with unified organisms from which there has been 


THE BEAUTY OF ANIMAL LIFE 413 


gradually sifted out all that was in any degree discordant 
or contradictory. A living creature leading an independ- 
ent life is a viable unity; and this is, we believe, the deep 
reason why it is also an artistic unity. Some animals are 
more integrated than others, with more unified and har- 
monious constitutions than others, and thus there will be 
different degrees of beauty. 

We adhere to the thesis that all wild animals, fully 
formed, living an independent life, and not tampered with 
by man, have this quality of beauty which excites in us the 
zesthetic emotion. For we have not been able to get be- 
yond the familiar definition of the beautiful: ‘‘A thing of 
beauty is a joy for ever.”’ Exceptions must be made for 
some domesticated animals, which have become ugly 
under man’s egis, for some half-finished or embryonic 
stages (which are usually hidden away), and for thorough- 
going internal parasites that live a drifting life of ease. 
But these exceptions seem to us to strengthen our thesis— 
that all free-living, fully-formed wild creatures have the 
quality of beauty. The esthetic emotion is our affair, it 
is subjective; we enhance it with thoughts and fancies, 
and these are obviously human. 

No doubt there is easy beauty and difficult beauty. It 
is easy to attain to some degree of admiration for a pea- 
cock’s tail; it is perhaps less easy to see the beauty of a 
grotesque like a puffin. Just as with pictures, some dis- 
cipline is needed. Many people are quite honest in deny- 
ing beauty to the hippopotamus, but they have not seen 
it with the eyes of the author of the Book of Job: 


Great behemoth, see him with his ruddy hide, in the shade 
of the lotuses, in the covert of the reeds and fens. His 
strength is in his loins; his force is in the sinews of his belly; the 
muscles of his thighs are knit together. His bones are pipes of 
brass; his limbs are like bars of iron; heis the chief of the ways 
of God. 


414 SCIENCE, OLD AND NEW 


We cannot see much of the beauty of an animal against 
which we have a strong prejudice, as against a snake or a 
stinging jellyfish. We must not expect every animal to 
be conventionally handsome; the point is whether it is an 
artistic unity. Thus a chameleon or a sea-horse is a 
grotesque, but no artist would for a moment think of 
either as ugly. Such libellous names as Moloch horridus 
indicate a careless acceptance of entirely conventional 
prejudice. On the other hand, we must welcome a change 
that has set in of recent years—the recognition of the 
beauty of very common creatures which crowd about our 
doors. We are learning the lesson of St. Peter’s house-top 
vision. 


LI 


NATURAL HISTORY AND MEDICINE 


415 





NATURAL HISTORY AND MEDICINE 


WHEN doctors dealt with animal simples and plant 
simples they had to be naturalists, and another ancient 
link was the leech, whose name became mixed up with the 
physician’s. Most of the old animal prescriptions seem to 
be quite superstitious: the dust of a dried magpie was pre- 
scribed for epilepsy and the rheumatic patient was told to 
take a black cat to bed with him, because it is rich in cura- 
tive electricity. But some of the old animal prescriptions 
have a smack of reasonableness. Thus, decoctions of ants, 
abounding in formic acid, might have antiseptic value; 
getting badly stung with bees might be of some use in 
rheumatism; and a diet of snails, with their copious diges- 
tive ferments, might have some virtue. Since the time of 
Aristotle dried toad and ashes of toad have been used in 
medicine, and we now know that the alkaloid poison called 
phrynin which exudes on the toad’s skin has, when in- 
jected, a rapid effect on the contraction of the arterioles, 
the blood pressure, and the beat of the heart. In such 
cases the old prescriptions seem to be on a plane quite 
different from that of the type represented by eating a 
lizard to cure leprosy. 


Treatment of Snake-bite 


In regard to snake-bite, some of the old prescriptions 
are very interesting. Thus the natives of some countries 


417 


418 SCIENCE, OLD AND NEW 


have been in the habit of drinking diluted snake poison to 
make themselves immune—and this is not very far away 
from the modern method of counteracting the poison by 
means of an anti-toxin serum prepared from a snake-bitten 
animal. In other native remedies the bile of the snake 
bulks largely, and it has been proved of recent years that 
the adder, for instance, actually carries about in the bile 
of its gall-bladder an antidote to its own poison. Some- 
thing chemically near the cholesterin of the bile is found 
in the roots of certain plants, and we find snake-bitten 
natives chewing these roots! So it is not wise to 
smile too loudly at all the old-fashioned animal pre- 
scriptions. 

Of course we must smile at the old advice given to the 
coward that he should eat the raw heart of a lion, or to the 
lethargic that he should dine on the brains of a ram, or to 
the jaundiced that he should try the liver of a fox. And 
yet are these not like adumbrations of the modern treat- 
ment of patients with defective or disturbed thyroid gland 
activity? For to them there is administered in some 
form or other the thyroid of sheep or calf. 


Protozoology 


The twentieth century has seen the establishment of 
many links between Natural History and Medicine, and it 
is interesting to bring a few of them together. Thus there 
has developed in a surprisingly short time a vigorous 
science of Protozoology which has on its medical side 
to do with the disease-causing réle of many of the 
simplest animals or Protozoa. This new science has its 
laboratories, professors, and journals; it is becoming as 
important as Bacteriology. It is enough to mention three 
diseases which Protozoa cause—malaria, sleeping sickness, 
and syphilis. Talking of microbes leads us also to note 
that Metchnikoff’s doctrine of phagocytosis—the rdle of 


NATURAL HISTORY AND MEDICINE 419 


amoeboid blood-corpuscles in engulfing and digesting 
virulent intruders—was to begin with a zoological in- 
vestigation. 


Medical Entomology 


Closely associated with the development of Protozoology 
has been the advance of medical entomology. For there 
has been great insight into the part played by insects (and 
some of their distant relatives like ticks) in fostering and 
distributing disease-organisms. Long ago the peasants 
said: “‘ Many mosquitoes, much malaria” and now we know 
how true thisis. The mosquito is the nurse of the malaria 
organism and there is no malaria in man except through 
mosquito-bites. To suffocate the larval mosquitoes in the 
pools a little petrol or paraffin is poured on, forming a sur- 
face film to which the young insect cannot adhere with its 
respiratory tube; and here we see that the effective 
method of checking malaria by drowning the mosquito- 
larve depends on a little zoological knowledge of the 
respiration of aquatic insects. 


Parasitology 


The same point may be illustrated in regard to the 
Guinea Worm. This thread-like worm was probably the 
‘Fiery Serpent”’ that troubled the Children of Israel when 
journeying in the desert. The female may be one to six 
feet in length; the male has been rarely seen. The juvenile 
stages are passed inside a small water-flea which is swal- 
lowed in unfiltered water. The adult female parasite 
tends to take up its position underneath man’s skin, where’ 
it twists into a coil, and often forms an abscess or an ugly 
sore. Till recently the usual procedure was to coax out a 
small piece of the worm, which is like thin twine, and twist 
it round a strip of wood. Gradually and carefully the 
whole worm was uncoiled, but it took time. Nowadays 


420 SCIENCE, OLD AND NEW 


the patient sits with his feet or arm in water for hours on 
end, and the worm comes out of herself. Now this im- 
proved method depends on a zoological understanding of 
what the female worm is seeking in coming near the sur- 
face of man’s body. She is trying to emerge into the 
water where the next generation begins. 

One of the formidable worms of warm countries, such as 
Egypt, is Bilharzia, a peculiar kind of fluke, two species of 
which frequent the alimentary canal or the kidney region 
of man. They cause great pain because the sharp edges 
of the microscopic eggs cut into the walls of the blood- 
vessels and the like when the patient moves. In the early 
years of the war, Dr. Leiper discovered the life-history of 
this formidable and common parasite, showing that the 
juvenile stages are passed inside certain fresh-water snails 
and that they enter man (or some other host) through 
lesions in the skin. We understand at once why Bilharzia 
should be particularly common in children, for they are 
fond of wading in the water; and in washerwomen and 
those who water the gardens; and why our soldiers should 
have been infected after bathing. To remove obscurities 
is the first aim of science, but Dr. Leiper did more. He 
showed how the disease could be checked. Thus the 
microscopic larve cannot live for more than thirty-six 
hours in drawn water that is kept quite still; and they are 
baulked by thoroughly good filters. This is one of the 
finest instances of zoology helping medicine. 

It is probably safe to say that one of the four biggest 
and heaviest clouds that have darkened the sky for man 
is that due to hookworm, a name given to several kinds of 
intestinal threadworms. They cause anemia, weakness, 
lethargy, and despair—the ‘‘tropical depression’’ often 
deplored by missionaries, explorers, and colonists. But 
the zoologist has shown how the eggs pass from man to 
the soil and develop there into larve which enter man 
through the skin; and the hookworm campaign waged in 


NATURAL HISTORY AND MEDICINE 421 


many parts of the world by the Rockefeller Institute has 
shown that if we could only persuade the natives that 
simple sanitation is life-saving, the cloud would entirely lift. 


Vital Linkages 


In great measure what is happening is that medical 
science is gripping the central zoological idea of vital 
linkages in the web of life. How are mosquito-larve to be 
killed off in Indian tanks for drinking-water, where the 
paraffin method is obviously impossible? By introducing 
little fishes called ‘‘millions’”’ which devour the larve and 
do no harm. ‘Ye gods and little fishes!” Where there 
are many cats there are fewer rats, and therefore less 
chance of man being bitten by a rat-flea with its mouth- 
parts fouled with the bacillus of the bubonic plague, which 
is at home in the rat. Professor Patrick Geddes suggests 
that if there were a dovecot in the yard of the mill, where 
the workers have their mid-day meal, the pigeons would 
pick up the crumbs, which always attract rats, there would 
be less chance of bites from the rat-flea, and the dread 
journey of the bacillus of the plague (the old ‘‘black 
death’’) would perhaps never begin. 

There are many links between zoology and medicine 
which are not less important than those we have men- 
tioned. Thus the new lore of unit characters and their 
Mendelian inheritance is changing the attitude of medical 
science to the heredity of disease, and there is quite 
extraordinary suggestiveness in the zoological facts bear- 
ing on the influence of nurture (alimentary, functional, 
and environmental) on the development and growth of 
the individual. 


Links Still to be Welded 


But great as have been the services of zoology to medi- 
cine, the probability is that there are greater yet to come. 


422 SCIENCE, OLD AND NEW 


Can one read Professor Hodge’s story of the worker-bee’s 
brain without feeling that there is in it something big for 
medicine? The busy bee improves the shining hour, but 
the shining hour does not improve the busy bee! Its 
brain-cells go steadily out of gear, and the summer bee 
has a very short life. Careful microscopical examination 
shows that there is in animals (1) nerve-tiredness to which 
rest and sleep bring recuperation; that there is (2) nerve- 
fag from which recovery is possible but difficult; and that 
there is (3) nerve-fatigue which means a fatal cell-collapse. 
And that is what the worker-bee dies of. 

Then there is Dr. Werber’s contribution to the problem 
of the origin of monstrosities. A little butyric acid in- 
duces extraordinary monstrosities in the head-end of 
American top-minnows. It dislocates and in part disturbs 
the germinal material of the head. But what respectable 
embryo could ever be influenced by butyric acid? The 
answer is that when something goes wrong with the 
chemical routine dealing with carbohydrate food, there 
may be a formation of butyric acid as a by-product. And 
butyric acid in the blood of the mammalian mother might 
seep through to the young embryo in the womb and induce 
monstrosities. 

Or take this as a final illustration. It is well known that 
the eggs of many animals—from sea-urchin to frog—can 
be launched on the voyage of development without being 
fertilised. By using various stimuli and then restoring the 
excited egg to normal conditions, there comes about arti- 
ficial parthenogenesis. It is also well known that a lost 
part—the arm of a starfish, or the leg of a crab, or the tail 
of a lizard—can be readily regrown. There is intense re- 
generative activity at the area of breakage. Then, again, 
it is a familiar fact that the salivary juice of a gall-fly’s 
larva, developing in the tissue of a leaf or shoot, incites a 
wonderful gall-growth, such as an ‘‘oak-apple.”’ Now let 
us suppose we could saturate ourselves in the facts along 


NATURAL HISTORY AND MEDICINE 423 


these three lines of zoological investigation, and put our 
best brains into reflecting on the data, might we not per- 
haps get a gleam of light on the dark problem of cancer? 
The links between Natural History and Medicine require 
to be tightened, not slackened, multiplied not reduced. 
New contacts between sciences are always rewarding. 






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THE NEW NATURAL HISTORY 


In byegone days, in more than one Scottish University 
there was a Chair of ‘‘Civil and Natural History.”” These 
were the days when the professor took for his subject not 
only the domain of things but also the realm of organisms, 
and also without any embarrassment threw in the king- 
dom of man. But in the course of time it was found de- 
sirable to knock off Civil History— there were would-be 
professors desirous of chairs—and Natural History came 
to mean the study of the whole outer world, human af- 
fairs excepted. It was still a great field! Later on came 
the inevitable cleavage between the sciences—more or 
less exact—of chemistry and physics, and the sciences— 
less or more exact—of botany and zoology. Geology, 
with a finger in both pies, kept close for many years to 
Zoology, and it was not till 1899 in the University of 
Aberdeen, for instance, that Natural History, shorn of 
much of its glory, became, for practical purposes, Zoology; 
for Botany had long previously separated itself off, thanks 
partly to the egis of Medicine, which, having disowned 
“‘animal simples,” clung the more tenaciously to phar- 
maceutical plants. Thus Natural History came to be a 
synonym for Zoology, as apart from Botany, and still 
more apart from Geology. This remains the most frequent 
usage; and it should die, for it is useless. 


Meaning of Natural History 


There is something very fine in the old idea of ‘‘ Natural 
History’’—that there is but one great subject of concrete 


427 


428 SCIENCE, OLD AND NEW 


study—the Order of Nature. But we cannot revive the 
term ‘‘Natural History” along that line; it is more prac- 
tical to lay emphasis on the correlation of the sciences, 
which Principal Caird saw so clearly from the synoptic, 
philosophical side. While we may be justifiably reserved 
in regard to the unity of science, for that implies an orches- 
tration of concepts that has not yet been attained, we 
are all agreed as to the unity of aim, which is the under- 
standing and, if possible, mastery of what goes on in 
Nature. 

But there is much to be said for retaining the old- 
fashioned term Natural History as a label for the study of 
habits and surroundings, as a synonym for what is often 
called ecology or bionomics. There is certainly need for a 
name for what a great zoologist used to call ‘‘the higher 
physiology,” the physiology of organisms as contrasted 
with the physiology of organs. Natural History is the 
study of living creatures as intact unities in their natural 
environment. It is the study of the everyday life of caring 
for self and caring for others. It is the study of habits and 
inter-relations; and Zoology and Botany apart from 
Natural History lose no small part of their charm and 
significance. 


Changes in Natural History 


It is a familiar fact that the aspect of a science some- 
times changes in a single generation, and the question we 
wish to ask is how Natural History has been changing 
since pre-Darwinian days. How does the Natural History 
of Mr. Beebe differ from that of Gilbert White? Many of 
us have become painfully aware of the changes in, say, 
Chemistry and Physiology, since we began to study them: 
there has also been a great change in Natural History, 
and it is interesting to analyse this. A change in a science 
may be due to new facts, such as radio-activity; or to new 


THE NEW NATURAL HISTORY .- 429 


ideas, such as evolution and the transformation of energy; 
or to new contacts, as when psychology joined hands with 
physiology; or to new methods, such as those involved, 
for instance, in microscope and spectroscope. All these 
kinds of influences have played upon Natural History, and 
there has been a process of ripening. Childish things have 
been put aside and Natural History has gained in serious- 
ness of purpose and in dignity. 


The Web of Life 


One of the most marked changes is that the idea of the 
correlation of organisms in the web of life has become the 
centre of Natural History. This is largely due to Darwin. 
Nothing lives or dies to itself. Everything, as John Locke 
said, isa retainer to some other part of Nature. The earth- 
worms plough the fields; the bees and the flowers are hand 
and glove; the mistle-thrush plants the mistletoe; the min- 
now nurses the mussel; the water wagtail helps the sheep- 
farmer; and the squirrel has its share in making the harvest 
a success. Suppose the glory that was Greece was in part 
dimmed by the obtrusion of malaria, as some historians 
say; the disease is sown by mosquitoes; the aquatic larval 
stages are very effectively checked by minnows. Once 
more, ‘‘ye gods and little fishes!”’ 


Precise Study of Behaviour 


Another change of a welcome kind is evident in regard 
to the whole study of animal behaviour. In old days the 
interpretation that was put on a piece of animal behaviour 
was very largely dependent on the observer’s tempera- 
ment. If he was generous and what William James called 
‘“‘tender-minded,”’ he read the man into the beast without 
hindrance. Every mammal was a Brer Rabbit and a 
honey bee a mathematical genius. But if the observer 


430 SCIENCE, OLD AND NEW 


was parsimonious and accustomed to use William of Oc- 
cam’s razor, being what James called ‘‘tough-minded,”’ 
he set his face sternly against all anthropomorphism and 
reduced the animal to the level of an automatic machine. 
In shunning the Scylla of anthropomorphism, the observer 
fell into the Charybdis of a psychic behaviourism, or vice 
versa. Now we have become more precise and critical, 
thanks largely to the work of Lloyd Morgan and Jacques 
Loeb, working from different ends. There is a recognition 
of a long series of kinds of activity, from reflex actions to 
rational conduct, arranged as branches from an ascending 
curve; and no act is ascribed to a higher mental faculty if 
it can be satisfactorily described in terms of a lower. 
Comparative psychology has emerged. The word instinct 
is no longer used by the naturalist in six senses. 


Evolutionism 


Another set of changes is due to the evolution theory. 
The affairs of life are seen in a historical setting. Every- 
thing is an antiquity. Thus the naturalist looks back to 
the three great invasions of the dry land by aquatic ani- 
mals, and traces in present-day habits the adjustments 
made by the conquerors of the new kingdom. The old 
method of simply liberating the eggs into the soft cradle 
of the water had to be departed from. Eggs on the sur- 
face of the ground would be dried up and devoured. So 
we bind together in a reasonable way all the arrangements 
by which terrestrial animals secure the safety of their eggs 
and young—nests on the trees, shafts sunk in the ground, 
silken bags that are hidden away or carried about, ex- 
ternal brood pockets and internal viviparity, a return to 
the water for this particular period, and the utilisation of 
another animal as acradle. These are only instances out 
of a long list of devices, which are unified by their histor- 
ical or evolutionary setting. 


THE NEW NATURAL HISTORY 431 


Adaptations 


The old naturalists were interested, as we are, in the 
adaptations of living creatures to the peculiar conditions 
of their existence, but they generally regarded these fit- 
nesses as endowments conferred, whereas we think of them 
as the long results of time, some of them still imperfect, 
some of them almost startling in their finish. There is a 
small Hymenopterous insect that lays its eggs in the 
larvee of gall-midges found in the wood-vessels of freshly 
cut trees. From the dorsal surface of its posterior body a 
remarkable hollow horn arises which extends forward 
over the thorax and ends just over the anterior eye-spot 
on the head. What an extraordinary structure! But its 
adaptive significance is clear. For it is confined to the 
females and it turns out to be a sheath for the protection 
of the extraordinarily elongated ovipositor which is able 
to reach down to the midge larve deeply ensconced in the 
vessels of the tree. The old Bridgewaterism was content 
to admire; the new Natural History tears its hair in the 
search for genetic description. 


Subtlety of Animate Nature 


Some of the old naturalists, men like Réaumur, had a 
keen appreciation of the subtlety of animate nature, but 
perhaps their successors have penetrated further. ‘‘I 
scrutinise life,’ Fabre said; and what revelations he has 
given us of the we intime of insects! His mantle has fallen 
on others. Mr. Beebe, travelling naturalist to the New 
York Zoological Society, is a good example. Recall, for 
instance, his vivid picture of the ways of the leaf-cutting 
ants, to which we have already referred. They climb 
trees, they cut off segments of leaf, they carry these to the 
underground nest, and make them into a green paste 
which is used as a culture-medium for a particular kind 


432 SCIENCE, OLD AND NEW 


of mould not found anywhere else. This mould forms the 
exclusive food of the leaf-cutters in their subterranean 
life. 

There are other interesting features in the new Natural 
History, indicative of a growing ripeness and precision. 
There is more definite correlation of the organism with its 
particular haunt and with the cycle of the seasons. The 
picture is less luridly red in colour than it used to be, for 
it has become clear that an answer-back that counts for 
much in the struggle for existence is caring for others. 
There is a growing appreciation of the amount of time and 
energy that animals devote to ends that are rather species- 
regarding than self-preservative. It is plain that in ordi- 
nary physiology and anatomy, embryology and genetics, 
little account is taken of the individual as such. We 
study features that are common to the species or type. 
But it is otherwise with Natural Hsitory; we must study 
the behaviour of the individual. And when we begin to 
see the animals we study not only as structural and func- 
tional unities, with an individual development and racial 
evolution behind them, but as animal personalities at 
various levels, as creatures with mental aspects, as agents 
that endeavour after well-being and share in their own 
further evolution, as threads in a quivering web of life, we 
begin to know what is meant by the new Natural History. 


Aard-vark, 222 
Aaronsohn, 350 

Acacia trees, 87 
Adamsia, 207 
Adaptations, 431 
Adjustor nerve-cells, 240 
Adrenalin, 153, 414 
Aesop prawn, 276 
Advance of science, 465 
African elephant, 331 
Agassiz, 254 

Age of the earth, 323 
Aggregation, 357 
Agricultural ants, 85 
Alder tree green-fly, 142 
Alcock, 207 

Alma, 20 

Amazon ants, 103 
Ambrosia, 127 
Ambrosia beetles, 126 
Ambrosia midges, 127 
American minnows, 422 
Amphiprion, 206 
Amphisbeenids, 23 
Anabolism, 251 
Andrews, C. W., 333, 335 
Aniline dyes, 404 
Animal colonies, 360 
Animal light, 307 
Animal products, 397 
Ant-hills, 363 
Anthropoid apes, 386 
Antlers, 171 

Ant-lion, 25 


Ants, 76, 361, 363, care of young 


among, 95 


communication between, 94 


daily life of, 94 
flower-gardens, of 86 
games of, 97 

guests of, 97 


mutiny among slaves of, 104 


INDEX 


nests of, 93 

pets of, 97 

raids of, 102 

rest of, 94 

slavery among, IOI 

toilet of, 93 
Ants and plants, 85 
Aphids, 96, III, 141, 231 
Arboreal man, 381, 388 
Arctic Tern, 261 
Argentine animals, 366 
Aristophanes, 70 
Arthropods, 281 
Ascent of man, 389 
Auxanometer, 290 
Aztec ants, 88 


B 


Bacillus of plague, 421 
Bacon, Francis, 403 
Bacteria, 218 
and luminescence, 315 
in aphids, 231 
in food canal, 231 
in cockroach, 229 
Bacterioids, 215 
Baker, Sir Samuel, 331 
Balgownie, 5 
Ballooning of spiders, 148 
Banfield, 206 
Barberry, 286 
Bat, 190 
Batten, Mortimer, 172 
Beauty, 409 
Beccari, 89 
Béche de mer, 221 
Bed-bug, 233 
Beebe, C. W., 123, 428, 431 
Bees, 422 
Bees and flowers, 131 
Beeswax, 139 
Beetles, burrowing, 22 
Beetles and bugs, 109 


433 


434 INDEX 


Behaviour of animals, 429 Caviare, 221 
of insects, 277 Cave animals, 61 
Behemoth, 413 Cecropia tree, 88 
Bell, Sir Charles, 377 Challenger Expedition, 262 
Bellerophon, 254 Chamois, 13 
Belt, 87, 123 Cheapest form of light, 309 
Belt’s corpuscles, 87 Chinese wax, 140 
Benthos epoch, 342 Chromatophores, 296 
Bernard, Claude, 291 Church, A. H., 341, 344, 345 
Berry, C. S., 239 Cicada, 119, 232 
Big tree, 261 Clothes moth, 222, 231 
Bilharzia, 420 Coal tar colours, 404 
Bilateral symmetry, 361 Coccidotrophus, 113 
Biological dichotomies, 251 Coccids, 112, 114 
Birds, first, 4 Coccus insects, 140 
Birds’ nest soup, 221 Cochineal insect 141, 232 
Bird hill, 29 Cochinellid beetle, 113 
Biscuit weevil, 221 Cock of the rock, 182 
Bite of gnat, 232 Cockroach, 229 
Black ant, 125 | Cold-blooded animals, 256 
Blackcock, 6 Cold light, 308 
Blackwell, 148 Collocalia, 221, 263 
Blake, William, 410 Colonial animals, 360 
Bloomfield, D., 239 Colonising the land, 339 
Blunden, E., 26 Coloration, 411 
Bonnet, 180 Colour cells, 277 
Bose, Sir J. C., 288, 289, 290, 291 Colour-change, 299, 300 
Boulenger, G. A., 50 Colour of trout, 295 
Bouton, 156 Colour-sense in fishes, 302 
Bouvier, E. L., 134, 135, 215, 277 in insects, 130 
Bower, F. O., 287, 340 Colour-vision in dancing mouse, 246 
Boyle, Robert, 310 Commensalism, 205 
Brehm, 238 Consanguinity, 370 
Brewster, Sir David, 154 Convoluta, 217 
Bromeliads, 41 Coral reef fishes, 303 
Bridgewater treatise, 377 Correlation of variations, 390 
Brook-leeches, 192 Courtship behaviour, 161 
Bryony, 262 of birds, 181 
Buchner, 230, 233, 317 colours of stickleback, 303 
Buller, A. H. R., 349 Cousin-marriages, 369 
Bull-frog, 70 Cow wheat, 57 
Burrowing animals, 23 Crabs, 207 
Butterwort, 286 Crescograph, 290 
Butyric acid, 422 Crickets, 117 
Buzz of insects, 120 Crocodiles, 71 
Cross-pollination, 351 
GS Cryptozoic life, 57 
Cuckoo, 222 
Cecilians, 23 Cuckoo-spit, 264 
Calling crab, 185 Cucujo, 317 
Call of the sea, 271 Cycads, 39 
Cancer, 42 Cypridina, 311 
Cannibalism, 112 
Capers, 142 D 
Carnivorous plants, 286 
Carr, Harvey A., 161 Dance of spiders, 184 
Caterpillars, 278 Dancing among birds and beasts, 
Cat and mouse, 237 181 


Cat’s eyes, 307 Dancing mouse, 243 


INDEX 


Darkness, influence of, 62 
Darwin, 134, 149, 183, 287, 377 
Darwin’s frog, 263 

Deafness of dancing mouse, 245 
Death-watch, 230 
Death-feigning, 47, 280 

De Bary, 213 

Deep sea, 64 

Delpino, 87 

Denudation in North America, 325 
Dero, 20 

Desman, I5 

Devices of animals, 263 

Diet, 22 

Differential sensitiveness, 279 
Digestion in plants, 287 
Digger wasps, 265 
Discosoma, 206 

Discovery and Invention, 403 
Disintegration, 360 

Doflein, 63 

Dolphin’s milk, 198 
Dominants, 371 

Doves, I61 

Drosophila, 218 

Drummer fishes, 69 
Drummond, Henry, 126 

Dry land, colonisation of, 430 
Dubois, R., 156 

Duckmole, 199 

Dwarf elephant, 332 


E 


Ear of dancing mouse, 245 
Earth, the cooling, 3 
Earthworms, 20, 224 
Ear-trumpet, 24, 25 
East, E. M., 369 
Edible animals, 397 
Edible birds’ nests, 221 
Educability, 247 
Education among animals, 192 
Edwards, Jonathan, 149 
Egg of guillemot, 34 
Elephant, pedigree of, 332 
Elephant’s trunk, 331 
Emction among animals, 182, 185 
Enchanter’s nightshade, 55 
Endogamy, 369 
Epiphytes, 41, 86 
Epizoic animals, 205 
Euglenids, 216 
Eupagurus, 207 
Everglades, 37 
Evolution, 267 

method of, 336, 343 

of plants, 341 

of sex, 252 


Evolutionism, 430 
Experimenting animals, 208 
Exudation, 77 


F 


Fabre, J. H., 349, 431 
Faulds, Henry, 380 
Feather parasites, 224 
Fierasfer, 205 

Fife, David, 354 

Fig, strangling, 40 
Fireflame, 318 

Fireflies, 308, 317 
Fishes, colours of, 296 
Flowers and insects, 131 
Florida, 37 
Fluorescence, 308 
Flying dragon, 327 
Forel, 93, 96, 101, 119, I 5 
Formic acid, 222 
Frisch, 301 
Froghoppers, 232, 264 
Frogs, 67 

Fruit-fly, 218 

Fungi in gnat, 232 
Fungus gardens, 126 
Fungus-growing ants, 123 


G 


Galls, 422 

Galton, 380 

Gammarids, 193 
Gardener insects, 123 
Gastric education, 200 
Geddes, Patrick, 421 
Geddes and Thomson, 252 
Geotropic, 273 

Germinal variations, 388 
Gnat, 232 

Goethe, 81, 261 

Golden Eagle, 14 
Goldfishes, 62 

Gossamer, 147 

Gossamer showers of, 149 
Gossamer spider, 266 
Grasshoppers, 118 

Great blackbacked gull, 34 
Grebe, great crested, 162 
Greek eagle, 263 

Green Amcebez, 217 

Green animals, 216 

Green Bell-animalcule, 216 
Green flies, 80 

Green Hydra, 217 

Green Protozoa, 216 
Gregarious animals, 361 
Groos, 238 


435 


430 


Ground pearls, 42 
Guanin, 298 
Guests of ants, 80 
Guillemot, 30 
Guinea-worm, 419 


H 


Haberlandt, 289 
Halley, Edmund, 326 
Handa Island, 29 
Hand, the human, 377 
Hand in evolution, 381, 388 
Hare, 190 
Harpagoxenus, 105 
Harvesting ants, 264 
Harvest mouse, 191 
Harvey, E. Newton, 307, 308, 309, 
310, 315, 316 
Hays, 353 
Heather, 214 
Helianthemum, 285 
Hermit-crab, 206, 262 
Hermon wheat, 350 
Herring gull, 226 
Hippopotamus, 413 
Hodge, Professor, 422 
Holmgren, 78 
Homo sapiens, 387 
Honey-pot ants, 96 
Hooker, 273 
Hookworm, 420 
House-worms, 278 
Howard, L. O., 278 
Huber, 101 
Hudson, W. H., 182, 183 
Hum of insects, 20 
Human evolution, factors in, 387 
Humming birds, 304 
Huxley, Julian, 162, 231 
Hybrids, 373 
Hydractinia, 208 
Hyrax, 15 


i 
Ibex, 14 
Imbauba tree, 88 
Infancy, importance of prolonged, 

390 

Infusorians, 218 
Indian elephant, 331 
Injurious animals, 399 
Inbreeding, 369 
Integration, 339 
Intelligence, 240 
Intelligent behaviour, 282 
Interrelations, 90 
Insects, behaviour of, 77 
Insect musicians, 117 


INDEX 


Instinctive behaviour, 240, 281 

Instinctive devices, 264 

Instinct and intelligence, 167 

Instinctive and intelligent, 256 

Instrumental music among insects, 
117 

Insurgent Mountain animals, 11, 13 

Inventiveness of animals, 261 

Irish deer, 173 

Iridocytes, 298 


i} 


Jacana, 183 

James, William, 256, 429 
Japanese pearls, 156 

Joly, 326 

Jones, D. F., 369 

Jones, F. Wood, 377, 378, 380 


K 


Kangaroo, 20, 190 
Katabolism, 251 
Katydids, 118 

Kea, 226 

Keith, Sir Arthur, 385 
Kelvin, Lord, 323, 403 
Kerner, 135 

Kitten’s play, 238 
Kittiwake, 30 
Knowledge, increase of, 403 
K6rnicke, 350 
Kotschy, 350 

Kurtus, 263 


L 


Lagaska, A., 353 

Land plants, 339 

Lankester, Sir Ray, 256, 396 
Langley, 308 

Larve of animals, 95 
Lavoisier, 404 

Leaf-cutter ants, 87, 123, 431 
Learning among insects, 135 
Leather-jackets, 22 

Le Couteur, 353 
Leguminous plants, 215 
Leiper, Dr. R. W., 420 
Lice, 233 

Lichens, 213 

Life, dawn of, 3 

Lightfoot, John, 385 

Lines on the hand, 379 
Linkages, 209 

Linneus, 296 

Lipochromes, 297 

Living lights, 307 
Lobworms, 124 


INDEX 


Locke, John, 209, 429 
Loeb, Jacques, 430 
Loggerhead turtles, 271 
Long-tailed tit, 191 

Love among animals, 192 
Luciferase, 310 
Luciferine, 310 

Lucretius, 390 
Luminescence, uses of, 311 
Luminescent animals, 307 
Luminescent organs, 309 
Luminous bacteria, 316 
Luminous cuttlefishes, 318 
Luminous fishes, 315 
Luminous insects, 317 


M 


Mackie, Dr., 339 
Macewen, Sir William, 173 
Maeterlinck, 277 
Mahonia, 286 
Maize, 371 
Malaria, 419 
Mammoth, 332 
Man, ancestry of, 386 
as crown of Nature, 395 
Evolution of, 390 
relations with animals, 396 
Mango tree, 89 
Manila Bay, 49 
Many-celled and single-celled, 254 
Marmot, 12 
Marquis wheat, 35 
Marsh plants, 38 
Marsupials, 199 
Masculinity, 172 
Mastodon, 334 
Maternal care, 190 
Maze experiments, 247 
McCook, Dr., 85, 363 
Meadow ant, 102 
Mealy bugs, 110 
Medicine and Natural History, 417 
Melanins, 297 
Melanophores, 299 
Melia, 207 
Mendelism, 371 
Meritherium, 332 
Metabolism, 251 
Metchnikoff, 418 
Mikimoto, 157 
Milk, 197 
composition of, 201 
Mimosa, 287 
Mimulus, 286 
Mole, 21 
Moller, 124 
Moloch, 414 


437 


Monotremes, 199 

Morgan, C. Lloyd, 430 
Mosasaurus, 48 

Mosquito, 119 

Mosquitoes and malaria, 419 
Mother of pearl, 155 
Mothering among animals, 189 
Motor nerve-cells, 241 
Mountain animals, 11 
Mountain beavers, 16 
Mountain birds, 11 

Mountain hare, 12 

Mount Hermon, 350 
Mourning-cloak butterfly, 279 
Mousing instinct, 239 
Movements of animals, 412 
Movements of plants, 287 
Mudfish, 22 

Multicellular animals, 339 
Murisier, 298 

Musical talent, evolution of, 390 
Mutual benefit society, 216 — 
Mycorhiza, 214 

Myrmecodia, 89 
Myrmecophily, 87, 110 


N 


Nacre, 155 
Nails, 380 
Natural History, 427 

and Medicine, 417 
Natural Selection, 389 
Neanderthal Man, 387 
Neger, 88, 128 
Neo-Lamarckian theory, 63 
Neolithic Man, 350, 351 
Nerves affecting colour-change, 301 
Nesting in pigeons, 165 
Nests, 19 
New Zealand Parrot, 226 
Nihlson-Ehle, 353 
Nitrogen, fixation of, 216 
Number of animals, 261 


O 





Oar-fish, 51 
(Ecotrophobiosis, 78 
Oddities of diet, 221 
Orchids, 40, 215 
Order of Nature, 428 
Organisata, 290 
Origin of land plants."339 
Opossum, 190 
Osborn, H. F., 334 
Os centrale, 378 
Osprey, 41 

Otter, 192 


438 INDEX 


Outbreeding, 369 
Oven bird, 19 


ae 
Paley, 377 
Paleomastodon, 333 
Palolo worm, 221 
Paradise Key, 37 
Parasitic animals, 398 
Parental care, 80 
Parkers Giles 7a 
Parthenogenesis, artificial, 422 
Partner Algze, 213, 216 
Partner Fungi, 214 
Partnership of beetles and bugs, 109 
Pearls, artificial, 154 
chemical composition of, 155 
different kinds of, 154 
Roman, 298 
and parasites, 157 
Peckham, Mr. and Mrs., observa- 
tions on spiders, 185 
Perez, 135 
Periwinkle, 22 
Pests, 399 
Pets of ants, 80 
Phagocytosis, 418 
Phalarope, 163 
Pierantoni, 319 
Pholas, 310, 315 
Photosynthesis, 216 
Piddock, 315 
Pigeons, courtship of, 161 
Pigeon’s milk, 199 
Pigment cells, 396, 397 
Piltdown skull, 387 
Pinguicula, 276 
Pithecanthropus, 387 
Plague, 421 
Plankton epoch, 342 
Plants and animals, 251, 291 
living in insects, 229 
movements of, 287 
Platurus, 49, 50 
Play of animals, 238 
of cat, 238 
Poisonous animals, 398 
Poison-tree, 38 
Pollen, 133 
Pollination, 132 
Polyergus, 103 
Pompilius, 282 
Porichthys, 312 
Praying palm, 288 
Prehistoric wheat, 356 
Preferential mating, 166 
Progress, 405 
Protective coloration, 302 
Proteus, 61, 62 


Protopterus, 22 
Protophyta, 359 
Protozoa, 359 

of soil, 21 

and Metazoa, 354 
Protozoology, 418 
Puffins, 321 
Punnett, 241 
Pyrophorus, 317 
Pyrosome, 308 
Pythonomorph, 47, 48 


: Rabbit, 190 


Races, crossing of, 373 
Radial and bilateral, 255 
Radio-activity, 324 
Radiolarians, 216 
Rainbow trout, 298 
Ramsay, Sir William, 405 
Raptiformica, 10 
Rat-flea, 421 

Rational selection, 390 
Rattlesnake, 71 
Rayleigh, Lord, 325 
Razor-bill, 30 

Réaumur, 140, 431 
Recessives, 371 

Red ant, 101 

Receptor nerve-cells, 240 
Red deer, 175 

Red Fife wheat, 354 
Redshanks, 181 

Reflex machines, 281 
Refugee mountain-animals, 11, 15 
Regan, C. Tate, 295 
Regeneration, 422 
Reibmayr, 369 
Reighard, Jacob, 303 
Reindeer, 171 

Relict mountain-animals, 11 
Rhynie fossils, 339 
Rhythms in animals, 278 
Riddle, Oscar, 161 

Rock creeper, 14 
Rockefeller Institute, 421 
Rock rose, 285 

Romanes, 237 

Rook, 67 

Root-tubercle, 215 
Roubaud, 75, 78, 278 
Ruffs, 181 

Rutherford, Sir E., 325 
Ruskin, 15 


Ss) 


Safford, W. E., 37 
Saltness of the Sea, 326 


INDEX 


Sambar, 175 
Sanderson, Sir John Burdon, 286 
Saunders, C. E., 353, 354 
Scales of fishes, 297 
Scale insects, 232 
Scalops, 24 
Scaly cuttlefish, 51 
Scavenger animals, 398 
Schaudinn, 232 
Schimper, 87 
Science and Life, 405 
and Invention, 403 
Schuchert, 326 
Scourie, 29 
Sea-anemone, 206, 262 
Sea-cucumber, 205, 224 
Sea-leeches, 193 
Sea-serpents, 50 
Sea-snakes, 47 
Sea swift, 221, 263 
Seaweeds, 343 
Sealing-wax, I4I 
Sedimentary rocks, 325 
Selous, Edmund, 181, 182 
Sensitiveness of plants, 288 
Sensitive plant, 280 
Septosporium, 125 
Serviformica, IOI, 102 
Sex, theory of, 253 
Shade plants, 51 
Shedding of antlers, 175 
Sheriff, Patrick, 353 
Sikora, 233 
Silveriness in fishes, 288 
Simpson, J. Y., 385 
Skull of elephant, 334 
Slavery, evolution of among ants, 
165 
Slime-fungus in ant, 229 
Snake-bite, 417 
Snow vole, 12 
Sociality, 359 
advantages of, 363 
conditions of, 365 
Social animals, 359 
wasps, 79 
Sollas, 326 
Song-box, 72 
Spalax, 24 
Spallanzani, 310 
Spiders, 42, 184 
maternal care among, 189 
Spinoza, 261 
Spiny ant-eater, 199 
Spoonbill, 431 
Spring, biology of, 67 
heralds of, 67 
Spur-winged lapwing, 183 
Squirrel, 190 


439 


Stags, 171 

Stead, David G. 302 
Stevenson, R. L., 40, 147 
Sticklebacks, 303 

Stoats, 7 

Stridulation, 118, 120 
Stringops, 23 
Strongylognathus, 105 
Struggle for existence, 39 
Subterranean animals, 21, 26 
Sumner, 302 

Sundew, 287 

Surinam toad, 69 
Swammerdam, 76 
Symbiosis, 213, 233, 317 
Synthetic chemistry, 404 


ah 


Tachigalia, 109 

Tailor ants, 77, 264 

Teeth of elephant, 355 
Termites, 78, 125, 222, 264, 363 
Testacella, 20 

Tetrabelodon, 333 
Thalassiophyta, 341 
Threadworms, 22 

Thrush, 267 

Tiger beetles, 264 

Toad’s poison, 417 

Tools among animals, 207, 265 
Transmigration, 341 

Trapdoor spiders, 266 

Tree creeper, 14 

Treub, 89 

Trial and Error, method of, 280 
Triple Alliance, 90, 109 
Troglodytes, 64 

Trophallaxis, 79 

Tropical depression, 420 
Tropisms, 274, 278 

Trout, colour of, 295 

Turtles, young, 272 
Typhlogobius, 64 
Typhlomolge, 62 

Typhlops, 23 


U 


Umbrella ants, 363 
Underworld, 19 
Useful animals, 400 


V 


Variability, 373 

of wheat, 352 
Velvet of antlers, 174 
Venus’ fly-trap, 286 


440 


Very, 308 

Vilmorin, 356 

Virgil, 352 

Volvox, 361 

Vries, H. de, 353 

Voice, 389 
evolution of, 69 
in Amphibians, 69 
in Reptiles, 71 


Warm-blooded animals, 256 
Warning colours, 302 
Wasmann, 77 
Wasps, 75, 277, 280, 282 
Water-bug, 280 
Water-ouzel, 15 
Water spider, 265 
Wax, 139 
chemical composition of, 146 
vegetable, 142 
Wax-moth, 224 
Web of Life, 147, 208, 429 
Wells, H. G., 399 
Werber, Dr., 422 
Wheatears, 30 
Wheat, history of, 349 
mummy, 350 
wild, 350 
Wheeler, W. M., 76, 78, 79, 80, 86, 
96, 109, 113 


INDEX 


White ants, 125, 363 
White, Gilbert, 428 
Whitman, C. O., 161, 164 
Whitney, 217 
Will to live, 261 
Wood Jon 22 

ood Jones, 377, 378, 380 
Woodpeckers, 222 be: 
Wordsworth, 409 
Worms, 20 
Wrist of Man, 378 


x 
Xerophyte epoch, 342 
Y; 


Yak, 13 

Yeast-cells, 218 

Yeasts, 223 

Yeasts in death-watch, 230 

Yerkes, Professor R. M., 239, 242, 
245, 246, 247 


Z 


Zoochlorelle, 216 
Zooxanthelle, 216 
Zoth, 244 


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